drm/amd/display: Check status from dpcd_get_tunneling_device_data

[WHAT & HOW]
dpcd_get_tunneling_device_data calls core_link_read_dpcd which can
fail. The status from core_link_read_dpcd should be checked and error
messages is printed in case of failures.

This fixes 1 UNUSED_VALUE issue reported by Coverity.

Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>