m4/ltp-fallocate.m4: add configure check for fallocate(2)

ltp-fallocate.m4: create a configure check for fallocate() syscall and
define the wrapper only when it's not available.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
diff --git a/configure.ac b/configure.ac
index ea6fa85..0004a55 100644
--- a/configure.ac
+++ b/configure.ac
@@ -172,5 +172,6 @@
 LTP_CHECK_CLONE_SUPPORTS_7_ARGS
 LTP_CHECK_MKDIRAT
 LTP_CHECK_FCHOWNAT
+LTP_CHECK_FALLOCATE
 
 AC_OUTPUT