selftests: kvm/x86: Export x86_family() for use outside of processor.c

Move this static inline function to processor.h, so that it can be
used in individual tests, as needed.

Opportunistically replace the bare 'unsigned' with 'unsigned int.'

Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220115052431.447232-5-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>