drm/amd/display: fix dp_retrieve_lttpr_cap() return value

gcc-13 notices a mismatch between the return type of dp_retrieve_lttpr_cap()
and the returned value:

drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c: In function 'dp_retrieve_lttpr_cap':
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:1465:24: error: implicit conversion from 'enum <anonymous>' to 'enum dc_status' [-Werror=enum-conversion]
 1465 |                 return false;
      |                        ^~~~~

Change the value to an actual dc_status code and remove the bogus
initialization that was apparently meant to get returned here.

Fixes: b473bd5f ("drm/amd/display: refine wake up aux in retrieve link caps")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/link/link_dp_capability.c

@@ -1455,14 +1455,14 @@ static bool dpcd_read_sink_ext_caps(struct dc_link *link)
 enum dc_status dp_retrieve_lttpr_cap(struct dc_link *link)
 {
 	uint8_t lttpr_dpcd_data[8];
-	enum dc_status status = DC_ERROR_UNEXPECTED;
-	bool is_lttpr_present = false;
+	enum dc_status status;
+	bool is_lttpr_present;
 
 	/* Logic to determine LTTPR support*/
 	bool vbios_lttpr_interop = link->dc->caps.vbios_lttpr_aware;
 
 	if (!vbios_lttpr_interop || !link->dc->caps.extended_aux_timeout_support)
-		return false;
+		return DC_ERROR_UNEXPECTED;
 
 	/* By reading LTTPR capability, RX assumes that we will enable
 	 * LTTPR extended aux timeout if LTTPR is present.