drm/display/dp: Define function to setup Extended wake time

drm/display/dp: Define function to setup Extended wake time

Extended wake timeout request helps to give additional
time by reading the DPCD register through which sink requests the
minimal amount of time required to wake the sink up.
Source  device shall keep retying the AUX tansaction till the
extended timeout that is being granted for LTTPRs from the
sink device.

--v2
-Add documentation [Dmitry]

Spec: DP v2.1 Section 3.6.12.3
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250122053358.1545039-3-suraj.kandpal@intel.com