drm/msm: remove unneeded variable ret

drm/msm: remove unneeded variable ret

This patch fix coccicheck warning:
drivers/gpu/drm/msm/dp/dp_link.c:848:5-8: Unneeded variable: "ret". Return "0" on line 880
Also remove unneeded function return value check.

Signed-off-by: Bernard Zhao <bernard@vivo.com>
Link: https://lore.kernel.org/r/20210407130654.3387-1-bernard@vivo.com
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>