drm/amd/display: Updated variable name.

[Why]
Fixed spelling error.

[How]
Changed "currnet_setting" to "current_setting".

Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Reviewed-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>