tests/kms_frontbuffer_tracking: Correctly handle debugfs errors

In commit 3f6ae7b19 ("igt/kms_frontbuffer_tracking: Keep the debugfs
dir around") we introduced custom variant of __igt_debugfs_read function
that fires assert when debugfs returns an error. Replace that assert
with proper error handling to allow use of errors like -ENODEV.

v2: allow only -ENODEV (Chris)

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
1 file changed