drm/rockchip: analogix_dp: Do not call Analogix code before bind

drm/rockchip: analogix_dp: Do not call Analogix code before bind

Driver callbacks, such as system suspend or resume can be called any
time, specifically they can be called before the component bind
callback. Let's use dp->adp pointer as a safeguard and skip calling
Analogix entry points if it is an ERR_PTR().

Signed-off-by: Tomasz Figa <[email protected]>
Signed-off-by: Thierry Escande <[email protected]>
Signed-off-by: Enric Balletbo i Serra <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Reviewed-by: Archit Taneja <[email protected]>
Signed-off-by: Andrzej Hajda <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]