drm/bridge: ti-sn65dsi86: Add local var for "dev" to simplify probe

Tiny cleanup for probe so we don't keep having to specify
"&client->dev" or "pdata->dev". No functional changes intended.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210423095743.v5.6.I83925d8ca228bdc5f55b17854c90754efc6a470e@changeid