hw/arm/virt: enable passing of EFI-stubbed kernel to guest UEFI firmware

hw/arm/virt: enable passing of EFI-stubbed kernel to guest UEFI firmware

The virt board already ensures mutual exclusion between -bios and -pflash
unit#0; we only need to set "bootinfo.firmware_loaded", introduced in the
previous patch, if either of those options was used to load the guest
firmware.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1419250305-31062-12-git-send-email-pbonzini@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>