drm/msm: remove checks for return value of drm_debugfs_create_files()

drm/msm: remove checks for return value of drm_debugfs_create_files()

Since commit 987d65d01356 (drm: debugfs: make
drm_debugfs_create_files() never fail), drm_debugfs_create_files never
fails and only returns 0. Therefore, the unnecessary checks for its
return value and error handling in various debugfs_init() functions in
drm/msm and have the functions return 0 directly.

v2: have debug functions return 0 instead of void to avoid build
breakage and ensure standalone compilation.

References: https://lists.freedesktop.org/archives/dri-devel/2020-February/257183.html
Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200310133121.27913-9-wambui.karugax@gmail.com