s390:tinyconfig fails to build with gcc 8.3.0.

arch/s390/include/asm/ctl_reg.h:52:2: error: impossible constraint in 'asm'
  asm volatile(       \
  ^~~
arch/s390/include/asm/ctl_reg.h:62:2: note: in expansion of macro '__ctl_store'
  __ctl_store(reg, cr, cr);
  ^~~~~~~~~~~
s390/include/asm/ctl_reg.h:41:2: error: impossible constraint in 'asm'
  asm volatile(       \
  ^~~
arch/s390/include/asm/ctl_reg.h:64:2:
note: in expansion of macro '__ctl_load'
  __ctl_load(reg, cr, cr);
  ^~~~~~~~~~

Marking __ctl_set_bit and __ctl_clear_bit as __always_inline fixes the
problem.

Fixes: 9012d011 ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>