drm/dp: do not read SET_POWER register during link power up

When trying to set the sink to D0 power mode, do not read the
DP_SET_POWER register as part of link power up API. It is
possible that the sink is in power down mode and might not
respond to this AUX read command till it exits the D3
power mode.

Change-Id: I7c65db8ec9eab1372b7043505dcd3ecd75d1a432
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>