s390: make __load_psw_mask work with clang

clang fails to use the %O and %R inline assembly modifiers
the same way as gcc, leading to build failures with every use
of __load_psw_mask():

/tmp/nmi-4a9f80.s: Assembler messages:
/tmp/nmi-4a9f80.s:571: Error: junk at end of line: `+8(160(%r11))'
/tmp/nmi-4a9f80.s:626: Error: junk at end of line: `+8(160(%r11))'

Replace these with a more conventional way of passing the addresses
that should work with both clang and gcc.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>