s390x/ioinst: Fix wrong MSCH alignment check on little endian

s390x/ioinst: Fix wrong MSCH alignment check on little endian

schib->pmcw.chars is 32bit, not 16bit. This fixes the kvm-unit-tests
"css" test, which fails with:

  FAIL: Channel Subsystem: measurement block format1: Unaligned MB origin:
  Program interrupt: expected(21) == received(0)

Because we end up not injecting an operand program exception.

Fixes: a54b8ac340c2 ("css: SCHIB measurement block origin must be aligned")
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: qemu-s390x@nongnu.org
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20210805143753.86520-1-david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>