drm/i915/dp: read Aux RD interval just before setting the FFE preset

drm/i915/dp: read Aux RD interval just before setting the FFE preset

Figure 3-52: 128b132b DP DPTC LANEx_CHANNEL_EQ_DONE Sequence of
DP2.1a spec.
After reading LANEx_CHANNEL_EQ_DONE, read the FFE presets.
AUX_RD_INTERVAL and then write the new FFE presets.

v4: Read AUX_RD_INTERVAL before get/set TX FFE preset (Jani)

Co-developed-by: Srikanth V NagaVenkata <nagavenkata.srikanth.v@intel.com>
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241011045825.2629469-1-arun.r.murthy@intel.com