qemuxmlconftest: x86_64: Bump 'firmware*' test cases to 'pc-i440fx-10.0'

qemuxmlconftest: x86_64: Bump 'firmware*' test cases to 'pc-i440fx-10.0'

New qemu is deprecating 'pc-i440fx-4.0-machine', update to the latest
released machine type.

Apart from the previous cases where we could use the aliased machine
type, the firmware auto-selection doesn't work properly for the
unexpanded 'pc' alias and thus we need to use a real machine type here.

Outside of tests a real machine type would be filled anyways, the use of
the alias happens only inside our '-latest' test suite.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>