drm/panel: Clean up S6E3HA2 config dependencies and fill help text

drm/panel: Clean up S6E3HA2 config dependencies and fill help text

As per the config name this Display IC features a DSI command-mode
interface (or the command to switch to video mode is not
known/documented) and does not use any of the video-mode helper
utilities, hence should not select VIDEOMODE_HELPERS. In addition it
uses devm_gpiod_get() and related functions from GPIOLIB.

Fixes: 779679d3c164 ("drm/panel: Add support for S6E3HA8 panel driver")
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260505-panel-clean-up-kconfig-dep-v2-3-9cc31d6e6919@ixit.cz