drm/panel: st7701: Decouple DSI and DRM parts

drm/panel: st7701: Decouple DSI and DRM parts

Split into a DSI-specific part and a DRM-specific part.

Additionally, use devm_add_action_or_reset() to simplify the flow,
and disable and unprepare the panel on cleanup.

Signed-off-by: Hironori KIKUCHI <kikuchan98@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240804061503.881283-3-kikuchan98@gmail.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240804061503.881283-3-kikuchan98@gmail.com