drm/panel: sw43408: Separate reset sequence into own function

drm/panel: sw43408: Separate reset sequence into own function

Splitting reset() from prepare() follows clean coding practices and lets
us potentially make reset optional in the future for flicker-less
takeover from a bootloader or framebuffer driver where the panel is
already configured.

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/20251214-pixel-3-v7-4-b1c0cf6f224d@ixit.cz