drm/arc: make arcgpu_debugfs_init() return 0.

drm/arc: make arcgpu_debugfs_init() return 0.

Since commit 8eacdfe59905 (drm: debugfs: make
drm_debugfs_create_files() never fail), drm_debugfs_create_files() never
fails and should return void. Therefore, remove its use as the
return value of arcpgu_debugfs_init() and have the latter function return
0 directly.

v2: convert the function to return 0 instead of void to avoid breaking
the build and ensure that this individual patch compiles properly.

References: https://lists.freedesktop.org/archives/dri-devel/2020-February/257183.html
Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.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/20200310133121.27913-6-wambui.karugax@gmail.com