s390: vfio-ap: include <asm/facility> for test_facility()
The driver uses test_facility(), but does not include the
corresponding include file explicitly. The driver currently builds
only thanks to the following include chain:
Files should not rely on such fragile implicit includes.
Signed-off-by: Petr Tesarik <ptesarik@suse.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Halil Pasic <pasic@linux.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>