testcases: Constify char *msg variable.

The parse_opts() now returns const char * instead of char * this commit
fixes all warnings caused by the change.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/testcases/kernel/syscalls/llseek/llseek02.c b/testcases/kernel/syscalls/llseek/llseek02.c
index 51e6c81..a6dae51 100644
--- a/testcases/kernel/syscalls/llseek/llseek02.c
+++ b/testcases/kernel/syscalls/llseek/llseek02.c
@@ -121,7 +121,7 @@
 int main(int ac, char **av)
 {
 	int lc;
-	char *msg;
+	const char *msg;
 	int fildes;		/* file handle for testfile */
 	int whence;		/* position of file handle in the file */
 	char *test_desc;	/* test specific error message */