linux-user/s390x: Save and restore psw.mask properly

linux-user/s390x: Save and restore psw.mask properly

At present, we're referencing env->psw.mask directly, which
fails to ensure that env->cc_op is incorporated or updated.
Use s390_cpu_{set_psw,get_psw_mask} to fix this.

Mirror the kernel's cleaning of the psw.mask in save_sigregs
and restore_sigregs.  Ignore PSW_MASK_RI for now, as qemu does
not support that.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Tested-by: jonathan.albrecht <jonathan.albrecht@linux.vnet.ibm.com>
Tested-by: <ruixin.bao@ibm.com>
Message-Id: <20210615030744.1252385-6-richard.henderson@linaro.org>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>