fix broken fallocate syscall in posix_fallocate

the syscall takes an extra flag argument which should be zero to meet
the POSIX requirements.

src/fcntl/posix_fallocate.c

@@ -3,6 +3,6 @@
 
 int posix_fallocate(int fd, off_t base, off_t len)
 {
-	return -__syscall(SYS_fallocate, fd, __SYSCALL_LL_O(base),
+	return -__syscall(SYS_fallocate, fd, 0, __SYSCALL_LL_E(base),
 		__SYSCALL_LL_E(len));
 }