[PATCH 7/9] drm/i915: Correct eDP panel power sequencing delay computations

[Keith Packard]

Store the panel power sequencing delays in the dp private structure,
rather than the global device structure. Who knows, maybe we'll get
more than one eDP device in the future.

Look at both the current hardware register settings and the VBT
specified panel power sequencing timings. Use the maximum of the two
delays, to make sure things work reliably. If there is no VBT data,
then those values will be initialized to zero, so we'll just use the
values as programmed in the hardware.

This patch computes power-up and power-down delays, rather than using
portions of the appropriate delay values as found in the hardware. The
eDP specified delay between raising VCC and communicating over the aux
channel includes both the power rise time (T1) and the aux channel
communication delay (T3). The eDP specified delay between powering
down the device and powering it back up includes both the power fall
time (T11) and the device idle time (T12).