s390/atomic: circumvent gcc 10 build regression

s390/atomic: circumvent gcc 10 build regression

Circumvent the following gcc 10 allyesconfig build regression:

  CC      drivers/leds/trigger/ledtrig-cpu.o
In file included from ./arch/s390/include/asm/bitops.h:39,
                 from ./include/linux/bitops.h:29,
                 from ./include/linux/kernel.h:12,
                 from drivers/leds/trigger/ledtrig-cpu.c:18:
./arch/s390/include/asm/atomic_ops.h: In function 'ledtrig_cpu':
./arch/s390/include/asm/atomic_ops.h:46:2: warning: 'asm' operand 1 probably does not match constraints
   46 |  asm volatile(       \
      |  ^~~
./arch/s390/include/asm/atomic_ops.h:53:2: note: in expansion of macro '__ATOMIC_CONST_OP'
   53 |  __ATOMIC_CONST_OP(op_name, op_type, op_string, "\n")  \
      |  ^~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:56:1: note: in expansion of macro '__ATOMIC_CONST_OPS'
   56 | __ATOMIC_CONST_OPS(__atomic_add_const, int, "asi")
      | ^~~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:46:2: error: impossible constraint in 'asm'
   46 |  asm volatile(       \
      |  ^~~
./arch/s390/include/asm/atomic_ops.h:53:2: note: in expansion of macro '__ATOMIC_CONST_OP'
   53 |  __ATOMIC_CONST_OP(op_name, op_type, op_string, "\n")  \
      |  ^~~~~~~~~~~~~~~~~
./arch/s390/include/asm/atomic_ops.h:56:1: note: in expansion of macro '__ATOMIC_CONST_OPS'
   56 | __ATOMIC_CONST_OPS(__atomic_add_const, int, "asi")
      | ^~~~~~~~~~~~~~~~~~
scripts/Makefile.build:280: recipe for target 'drivers/leds/trigger/ledtrig-cpu.o' failed

By swapping conditions as proposed here:
https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549318.html

Suggested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>