amdgpu/dm: Remove fb_location form fill_plane_attributes

We no longer set the framebuffer address here so this is now
dead code.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>