drm/bridge: ti-sn65dsi83: Optimize reset line toggling

Current code always sets reset line low in .pre_enable callback and
holds it low for 10ms. This is sub-optimal and increases the time
between enablement of the DSI83 and valid LVDS clock.

Rework the reset handling such that the reset line is held low for 10ms
both in probe() of the driver and .disable callback, which guarantees
that the reset line was always held low for more than 10ms and therefore
the reset line timing requirement is satisfied. Furthermore, move the
reset handling into .enable callback so the entire DSI83 initialization
is now in one place.

This reduces DSI83 enablement delay by up to 10ms.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211016210402.171595-1-marex@denx.de