target/s390x: Fix ICM with M3=0

target/s390x: Fix ICM with M3=0

When the mask is zero, access exceptions should still be recognized for
1 byte at the second-operand address. CC should be set to 0.

Cc: qemu-stable@nongnu.org
Fixes: e023e832d0ac ("s390x: translate engine for s390x CPU")
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230724082032.66864-5-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit a2025557ed4d8d5e6a4d0dd681717c390f51f5be)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>