drm/amd/display: Fix preferred link rate for NUTMEG

drm/amd/display: Fix preferred link rate for NUTMEG

When there is a preferred link rate setting, it needs to be
applied to both the current and initial link rate.
This was regressed by a "coding style" fix, which caused
the current link rate to not respect the preferred value.

This commit restores the functionality of NUTMEG,
the DP bridge encoder found on old APUs such as Kaveri.

Fixes: a62346043a89 ("drm/amd/display: Fix coding style issue")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5465
Cc: Chuanyu Tseng <Chuanyu.Tseng@amd.com>
Reviewed-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>