drm/i915/dp: Add FEC Enable Retry mechanism

drm/i915/dp: Add FEC Enable Retry mechanism

Currently, even though there is a bit to control FEC enable/disable
individually, the FEC Decode Enable sequence is sent by the SOC only
once TRANS_CONF enable is set. This ties the FEC enabling too tightly
to modeset and therefore cannot be re-issued (in case of failure)
without a modeset.

From PTL, FEC_DECODE_EN sequence can be sent to a DPRX independent
of TRANS_CONF enable. This allows us to re-issue an FEC_DECODE_EN
sequence without a modeset. Hence allowing us to have a retry
mechanism in case the DPRX does not respond with an FEC_ENABLE
within certain amount of time.

While at it, replace struct drm_i915_private with struct intel_display

v4:
 - More code refactor [Jani]
 - use struct intel_display [Jani]
 - Optimize logging [Jani]

v3:
 - Make the commit message more legible [Jani]
 - Refactor code to re-use existing code [Jani]
 - Do away with platform dependent FEC enable checks [Jani]

v2:
 - Refactor code to avoid duplication and improve readability [Jani]
 - In case of PTL, wait for FEC status directly after FEC enable [Srikanth]
 - Wait for FEC_ENABLE_LIVE_STATUS to be cleared before
   re-enabling FEC [Srikanth]

Signed-off-by: Chaitanya Kumar Borah <[email protected]>
Reviewed-by: Jani Nikula <[email protected]>
Signed-off-by: Suraj Kandpal <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]