KVM: s390: vsie: fix the length of APCB bitmap

KVM: s390: vsie: fix the length of APCB bitmap

bit_and() uses the count of bits as the woking length.
Fix the previous implementation and effectively use
the right bitmap size.

Fixes: 19fd83a64718 ("KVM: s390: vsie: allow CRYCB FORMAT-1")
Fixes: 56019f9aca22 ("KVM: s390: vsie: Allow CRYCB FORMAT-2")
Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/kvm/20230511094719.9691-1-pmorel@linux.ibm.com/
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>