microblaze: Enable futimesat syscall

Futimesat was disabled. LTP testing shows that MB has no
problem with this syscall.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/syscall_table.S

@@ -303,7 +303,7 @@ ENTRY(sys_call_table)
 	.long sys_mkdirat
 	.long sys_mknodat
 	.long sys_fchownat
-	.long sys_ni_syscall
+	.long sys_futimesat
 	.long sys_fstatat64		/* 300 */
 	.long sys_unlinkat
 	.long sys_renameat