drm/amd/display: Remove CR AUX RD Interval limit for LTTPR

[Why]
DP spec specifies that DPRX shall use the read interval in the
TRAINING_AUX_RD_INTERVAL_PHY_REPEATER LTTPR DPCD register. This
register's bit definition is the same as the AUX read interval register
for DPRX.

[How}
Remove logic which forces AUX read interval to 100us for repeaters when
in LTTPR non-transparent mode.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Wesley Chalmers <wesley.chalmers@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: George Shen <George.Shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>