isl/tests: Use a longer path for isl.h

The tests assumed that isl would be in the include path but that usually
isn't the case.  Instead, we usually have src/intel and you need to add an
"isl/" prefix.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/intel/isl/tests/isl_surf_get_image_offset_test.c

@@ -27,8 +27,8 @@
 #include <stdlib.h>
 
 #include "brw_device_info.h"
-#include "isl.h"
-#include "isl_priv.h"
+#include "isl/isl.h"
+#include "isl/isl_priv.h"
 
 #define BDW_GT2_DEVID 0x161a