qemuBuildCommandLine: Inline qemuCheckFips

qemuBuildCommandLine: Inline qemuCheckFips

Now that we store the state of the host FIPS mode setting in the qemu
driver object, we don't need to outsource the logic into
'qemuCheckFips'.

Additionally since we no longer support very old qemu's which would not
yet have --enable-fips we can drop the part of the comment about very
old qemus.

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