powerpc: Wire up sys_membarrier()

The selftest passes on 64-bit LE & BE, and 32-bit.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/systbl.h

@@ -369,3 +369,4 @@ SYSCALL_SPU(bpf)
 COMPAT_SYS(execveat)
 PPC64ONLY(switch_endian)
 SYSCALL_SPU(userfaultfd)
+SYSCALL_SPU(membarrier)

arch/powerpc/include/asm/unistd.h

@@ -12,7 +12,7 @@
 #include <uapi/asm/unistd.h>
 
 
-#define __NR_syscalls		365
+#define __NR_syscalls		366
 
 #define __NR__exit __NR_exit
 #define NR_syscalls	__NR_syscalls

arch/powerpc/include/uapi/asm/unistd.h

@@ -387,5 +387,6 @@
 #define __NR_execveat		362
 #define __NR_switch_endian	363
 #define __NR_userfaultfd	364
+#define __NR_membarrier		365
 
 #endif /* _UAPI_ASM_POWERPC_UNISTD_H_ */