syscalls/mprotect: Fix mmap() error checks.

The addr < 0 is always true. Make use of proper MAP_FAILED constant
instead.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/testcases/kernel/syscalls/mprotect/mprotect01.c b/testcases/kernel/syscalls/mprotect/mprotect01.c
index b781968..fef0df6 100644
--- a/testcases/kernel/syscalls/mprotect/mprotect01.c
+++ b/testcases/kernel/syscalls/mprotect/mprotect01.c
@@ -162,7 +162,7 @@
 	 * mmap the PAGESIZE bytes as read only.
 	 */
 	addr3 = mmap(0, PAGESIZE, PROT_READ, MAP_SHARED, fd, 0);
-	if (addr3 < 0)
+	if (addr3 == MAP_FAILED)
 		tst_brkm(TBROK, cleanup, "mmap failed");
 }
 
diff --git a/testcases/kernel/syscalls/mprotect/mprotect03.c b/testcases/kernel/syscalls/mprotect/mprotect03.c
index 49212f3..81a3296 100644
--- a/testcases/kernel/syscalls/mprotect/mprotect03.c
+++ b/testcases/kernel/syscalls/mprotect/mprotect03.c
@@ -87,7 +87,7 @@
 		 */
 		addr = mmap(0, strlen(buf), PROT_READ | PROT_WRITE, MAP_SHARED,
 			    fd, 0);
-		if (addr < 0)
+		if (addr == MAP_FAILED)
 			tst_brkm(TBROK, cleanup, "mmap failed");
 
 		/*