drm/bridge: ti-sn65dsi86: Use devm to do our runtime_disable

There's no devm_runtime_enable(), but it's easy to use
devm_add_action_or_reset() and means we don't need to worry about the
disable in our remove() routine or in error paths.

No functional changes intended by this change.

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.v5.4.I1e627eb5f316c0cf6595b120e6e262f5bf890300@changeid