drm/i915/cx0: Add step for programming msgbus timer

drm/i915/cx0: Add step for programming msgbus timer

There was a recent update in the BSpec adding an extra step to the PLL
enable sequence, which is for programming the msgbus timer. Since we
also touch PHY registers during hw readout, let's do the programming
when starting a transaction rather than only when doing the PLL enable
sequence.

This might be the missing step that was causing the timeouts
that we have recently seen during C20 SRAM register programming
sequences. With this in place, we shouldn't need the logic to bump the
timer thresholds, since now we have a documented value that should be
set peform programming the registers. As such, let's also remove
intel_cx0_bus_check_and_bump_timer(), but keep the part that checks if
hardware really detected a timeout, which might be useful debugging
information.

v2:
  - Use debug level instead of warning for the message notifying that
    the hardware did not detect the timeout. (Mika)
  - Got a new BSpec update clarifying that we need to program the msgbus
    timer of both PHY lanes. Update the changes to reflect that.
    (Gustavo)

BSpec: 64568
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230912155923.39494-1-gustavo.sousa@intel.com