msm: kgsl: Check the return value of sysfs functions

Do a WARN_ON check for sysfs_create_file and sysfs_create_bin_file to
avoid a compiler warning.

Fixes: 41b90d7b ("msm: kgsl: Remove a few unused device tree properties")
Change-Id: Ic0dedbadede06484faf0dde107a6cde08b89a40a
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>