drm/amd/display: Revert " drm/amd/display: Use channel_width = 2 for vram table 3.0"

[Description]
Revert commit fec05adc ("drm/amd/display: Use channel_width = 2 for vram table 3.0")
Because the issue is being fixed from VBIOS side.

Reviewed-by: Samson Tam <samson.tam@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>