s390x: snippets: Fix SET_PSW_NEW_ADDR macro

Let's store the psw mask instead of the address of the location where we
should load the mask from.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20230112154548.163021-5-frankja@linux.ibm.com
Message-Id: <20230112154548.163021-5-frankja@linux.ibm.com>