graphics_Gbm: Fix bo fd test

The dmabuf fd (which is what gbm_bo_get_fd returns) is different from
the device's fd. So test that we have a valid fd, but we can't do much
more than that.

BUG=none
TEST=ran the test

Change-Id: I01c9db4ef79fe59714612f833464cfdbba4ed8f5
Reviewed-on: https://chromium-review.googlesource.com/227452
Tested-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Ilja Friedel <ihf@chromium.org>
Commit-Queue: Stéphane Marchesin <marcheu@chromium.org>
diff --git a/client/site_tests/graphics_Gbm/src/gbmtest.c b/client/site_tests/graphics_Gbm/src/gbmtest.c
index 3f9b484..20e4bd8 100644
--- a/client/site_tests/graphics_Gbm/src/gbmtest.c
+++ b/client/site_tests/graphics_Gbm/src/gbmtest.c
@@ -90,7 +90,7 @@
 	CHECK(gbm_bo_get_width(bo) >= 0);
 	CHECK(gbm_bo_get_height(bo) >= 0);
 	CHECK(gbm_bo_get_stride(bo) >= gbm_bo_get_width(bo));
-	CHECK(gbm_bo_get_fd(bo) == fd);
+	CHECK(gbm_bo_get_fd(bo) > 0);
 
 	return 1;
 }