qemu: Relax os.loader->type check when validating domain

qemu: Relax os.loader->type check when validating domain

When validating a domain among all the checks there are two that
concern VIR_DOMAIN_LOADER_TYPE_PFLASH specifically. The first
check ensures that on x86 ACPI is enabled when UEFI is requested,
the second ensures that UEFI is used when ACPI is requested on
aarch64. However, check for UEFI is done by plain comparison of
def->os.loader->type which is insufficient because we have
def->os.firmware too.

NB, this wouldn't be a problem for active domain, because on
startup process def->os.loader->type gets filled by
qemuFirmwareEnableFeatures(), but that's not the case for
inactive domains.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1729604
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>