drm/amd/display: check for repeater when setting aux_rd_interval.

[Why]
When training with repeater the aux read interval must be set to
repeater specific aux_red_interval. This value is always 100us for CR.

[How]
Check for repeater when setting the aux_rd_interval in channel
equalization.
Use the right offset in the aux_rd_interval array

Signed-off-by: abdoulaye berthe <abdoulaye.berthe@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: George Shen <George.Shen@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>