FROMLIST: drm: bridge: analogix/dp: move hpd detect to connector detect function

FROMLIST: drm: bridge: analogix/dp: move hpd detect to connector detect function

This change just make a little clean to make code more like
drm core expect, move hdp detect code from bridge->enable(),
and place them into connector->detect().

Note: Gustavo Padovan try to remove the controller and phy
power on function in bind time at bellow commit:
	drm/exynos: do not start enabling DP at bind() phase

But for now the connector status don't hardcode to connected,
need to operate dp phy in .detect function, so we need to revert
parts if Gustavo Padovan's changes, add phy poweron
function in bind time.

(am from https://patchwork.kernel.org/patch/8312901/)

Change-Id: I0ed1be541210f85883477f1b2a88bd8d57e390d6
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>