drm/nouveau: make nouveau_drm_debugfs_init() return 0

drm/nouveau: make nouveau_drm_debugfs_init() return 0

Since 987d65d01356 (drm: debugfs: make
drm_debugfs_create_files() never fail), there is no need to ever check
for the the return value of debugfs_create_file() and
drm_debugfs_create_files(). Therefore, remove unnecessary checks and
error handling in nouveau_drm_debugfs_init() and have the function
return 0 directly.

v2: have nouveau_drm_debugfs_init() return 0 instead of void so as not
to introduce any build warnings to enable individual patch 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/20200310133121.27913-12-wambui.karugax@gmail.com