[S390] Wire up sys_fallocate.

This patch implements support of fallocate system call on s390(x)
platform.  A wrapper is added to address the issue which s390 ABI has with
the arguments of this system call.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/include/asm-s390/unistd.h b/include/asm-s390/unistd.h
index 790c1c5..f04acb2 100644
--- a/include/asm-s390/unistd.h
+++ b/include/asm-s390/unistd.h
@@ -251,7 +251,7 @@
 #define __NR_getcpu		311
 #define __NR_epoll_pwait	312
 #define __NR_utimes		313
-/* Number 314 is reserved for new sys_fallocate */
+#define __NR_fallocate		314
 #define __NR_utimensat		315
 #define __NR_signalfd		316
 #define __NR_timerfd		317