drm/amd/display/dc/dce/dce_aux: Remove unused function 'get_engine_type'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_aux.c:391:25: warning: no previous prototype for ‘get_engine_type’ [-Wmissing-prototypes]

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_aux.c

@@ -388,12 +388,6 @@ static enum aux_channel_operation_result get_channel_status(
 	}
 }
 
-enum i2caux_engine_type get_engine_type(
-		const struct dce_aux *engine)
-{
-	return I2CAUX_ENGINE_TYPE_AUX;
-}
-
 static bool acquire(
 	struct dce_aux *engine,
 	struct ddc *ddc)