pc-bios/s390-ccw: always build network bootloader

In the beginning, the network bootloader was considered experimental and
thus optional, but it is well established nowadays and configure always
checks for roms/SLOF before compiling pc-bios/s390-ccw.

Therefore, it makes sense to always build it together with the other
part of the s390-ccw bios.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

pc-bios/s390-ccw/Makefile

@@ -67,12 +67,7 @@ s390-ccw.img: s390-ccw.elf
 
 $(OBJECTS): Makefile
 
-ifneq ($(wildcard $(SRC_PATH)/../../roms/SLOF/lib/libnet),)
 include $(SRC_PATH)/netboot.mak
-else
-s390-netboot.img:
-	@echo "s390-netboot.img not built since roms/SLOF/ is not available."
-endif
 
 ALL_OBJS = $(sort $(OBJECTS) $(NETOBJS) $(LIBCOBJS) $(LIBNETOBJS))
 -include $(ALL_OBJS:%.o=%.d)