s390: remove 31 bit support

Remove the 31 bit support in order to reduce maintenance cost and
effectively remove dead code. Since a couple of years there is no
distribution left that comes with a 31 bit kernel.

The 31 bit kernel also has been broken since more than a year before
anybody noticed. In addition I added a removal warning to the kernel
shown at ipl for 5 minutes: a960062e58 ("s390: add 31 bit warning
message") which let everybody know about the plan to remove 31 bit
code. We didn't get any response.

Given that the last 31 bit only machine was introduced in 1999 let's
remove the code.
Anybody with 31 bit user space code can still use the compat mode.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/percpu.h

@@ -10,8 +10,6 @@
  */
 #define __my_cpu_offset S390_lowcore.percpu_offset
 
-#ifdef CONFIG_64BIT
-
 /*
  * For 64 bit module code, the module may be more than 4G above the
  * per cpu area, use weak definitions to force the compiler to
@@ -183,8 +181,6 @@
 #define this_cpu_cmpxchg_double_4 arch_this_cpu_cmpxchg_double
 #define this_cpu_cmpxchg_double_8 arch_this_cpu_cmpxchg_double
 
-#endif /* CONFIG_64BIT */
-
 #include <asm-generic/percpu.h>
 
 #endif /* __ARCH_S390_PERCPU__ */