igt/drv_hangman: Fix checking of strcasecmp against expectation

Comparing strcasecmp against a bool promotes the bool into an integer
and not force strcasecmp to be a bool. Since strcasecmp can return
negative or positive values for error (not a boolean!) we need to
convert into a boolean before comparing against our expectation.

Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/tests/drv_hangman.c b/tests/drv_hangman.c
index bc20e70..51bdbda 100644
--- a/tests/drv_hangman.c
+++ b/tests/drv_hangman.c
@@ -58,7 +58,7 @@
 	error = igt_sysfs_get(sysfs, "error");
 	igt_assert(error);
 
-	igt_assert_f(strcasecmp(error, s) != expect,
+	igt_assert_f(!!strcasecmp(error, s) != expect,
 		     "contents of error: '%s' (expected %s '%s')\n",
 		     error, expect ? "": "not", s);