drm/amd/display: Use context parameters to enable FBC

drm/amd/display: Use context parameters to enable FBC

[What]
FBC fails to get enabled when switched between LINEAR(console/VT)
and non-LINEAR(GUI) based rendering due to default value of
tiling info stored in the current_state which is used for deciding
whether or not to turn FBC on or off.

[How]
Use context structure's tiling information which is coherant with
the screen updates.

Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>