drm/amd/display: Remove unused function

The get_engine_type is never used in the code, for this reason, this
commit drops this function.

Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>

drivers/gpu/drm/amd/display/dc/inc/hw/aux_engine.h

@@ -172,8 +172,6 @@ struct aux_engine_funcs {
 		struct aux_engine *engine,
 		uint8_t *returned_bytes);
 	bool (*is_engine_available)(struct aux_engine *engine);
-	enum i2caux_engine_type (*get_engine_type)(
-		const struct aux_engine *engine);
 	bool (*acquire)(
 		struct aux_engine *engine,
 		struct ddc *ddc);