drm/amd/display: Remove static property from decide_edp_link_settings

[Why & How]
Static cleanup for eDP ILR Support.

Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Acked-by: Bindu Ramamurthy <bindur12@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>