hw: Default -drive to if=none instead of ide when ide cannot work

Block backends defined with -drive if=ide are meant to be picked up by
machine initialization code: a suitable frontend gets created and
wired up automatically.

if=ide drives not picked up that way can still be used with -device as
if they had if=none, but that's unclean and best avoided.  Unused ones
produce an "Orphaned drive without device" warning.

-drive parameter "if" is optional, and the default depends on the
machine type.  If a machine type doesn't specify a default, the
default is "ide".

Many machine types implicitly default to if=ide that way, even though
they don't actually have an IDE controller.  This makes no sense.

Change the implicit default to if=none.  Affected machines:

* all targets: none
* aarch64/arm: akita ast2500 canon cheetah collie connex imx25
  integratorcp kzm lm3s6965evb lm3s811evb mainstone musicpal n800 n810
  netduino2 nuri palmetto realview romulus sabrelite smdkc210 sx1 sx1
  verdex z2
* cris: axis-dev88
* i386/x86_64: xenpv
* lm32: lm32-evr lm32-uclinux milkymist
* m68k: an5206 dummy mcf5208evb
* microblaze/microblazeel: petalogix-ml605 petalogix-s3adsp1800
* mips/mips64/mips64el/mipsel: mipssim
* moxie: moxiesim
* or32: or32-sim
* ppc/ppc64/ppcemb: bamboo ref405ep taihu virtex-ml507
* ppc/ppc64: mpc8544ds ppce500
* sh4/sh4eb: shix
* sparc: leon3_generic
* sparc64: niagara
* tricore: tricore_testboard
* unicore32: puv3
* xtensa/xtensaeb: kc705 lx200 lx60 ml605 sim

None of these machines have an IDE controller, let alone code to
honor if=ide.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm@nongnu.org
Cc: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: xen-devel@lists.xensource.com
Cc: Michael Walle <michael@walle.cc>
Cc: Laurent Vivier <laurent@vivier.eu>
Cc: Anthony Green <green@moxielogic.com>
Cc: Jia Liu <proljc@gmail.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: qemu-ppc@nongnu.org
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Fabien Chouteau <chouteau@adacore.com>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Artyom Tarasenko <atar4qemu@gmail.com>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-By: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1487153147-11530-4-git-send-email-armbru@redhat.com>

include/sysemu/blockdev.h

@@ -19,12 +19,11 @@ void blockdev_auto_del(BlockBackend *blk);
 typedef enum {
     IF_DEFAULT = -1,            /* for use with drive_add() only */
     /*
-     * IF_IDE must be zero, because we want MachineClass member
-     * block_default_type to default-initialize to IF_IDE
+     * IF_NONE must be zero, because we want MachineClass member
+     * block_default_type to default-initialize to IF_NONE
      */
-    IF_IDE = 0,
-    IF_NONE,
-    IF_SCSI, IF_FLOPPY, IF_PFLASH, IF_MTD, IF_SD, IF_VIRTIO, IF_XEN,
+    IF_NONE = 0,
+    IF_IDE, IF_SCSI, IF_FLOPPY, IF_PFLASH, IF_MTD, IF_SD, IF_VIRTIO, IF_XEN,
     IF_COUNT
 } BlockInterfaceType;