s390x/css: fix PMCW invalid mask

s390x/css: fix PMCW invalid mask

Previously, we required bits 5, 6 and 7 to be zero (0x07 == 0b111). But,
as per the principles of operation, bit 5 is ignored in MSCH and bits 0,
1, 6 and 7 need to be zero.

As both PMCW_FLAGS_MASK_INVALID and ioinst_schib_valid() are only used
by ioinst_handle_msch(), adjust the mask accordingly.

Fixes: db1c8f53bfb1 ("s390: Channel I/O basic definitions.")
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20211216131657.1057978-1-nrb@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>