HV: modify HV RAM and serial config for apl-nuc

- To support grub multiboot for nuc6cayh, we should put hv ram start
  at a suitable address;

- Enable HSUART controller at PCI 0:18.0 as HV serail port;

Tracked-On: #3214

Signed-off-by: Victor Sun <victor.sun@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: jsun26intel

hypervisor/arch/x86/configs/nuc6cayh.config

@@ -1,3 +1,7 @@
 # Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 CONFIG_BOARD="nuc6cayh"
-CONFIG_SERIAL_LEGACY=y
+# There is no ready-made serial connector on NUC6CAYH, but developer could
+# enable HSUART at PCI 0:18.0 by soldering Tx/Rx wires from M.2 connector;
+CONFIG_SERIAL_PCI=y
+CONFIG_SERIAL_PCI_BDF="0:18.0"
+CONFIG_HV_RAM_START=0x12200000