drm/nouveau/fuse/gm107: simplify the return logic

Spotted by coccinelle:
drivers/gpu/drm/nouveau/core/subdev/fuse/gm107.c:50:5-8: WARNING: end returns can be simpified

Signed-off-by: Martin Peres <martin.peres@free.fr>
Reviewed-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>