drm/amd/display: Add link encoding to timing BW calculation parameters

[Why]
There certain cases where the timing BW is dependent on the type of link
encoding in use. Thus to calculate the correct BW required for a given
timing, the link encoding should be added as a parameter.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>