drm/amd/display: Remove unnecessary error message

[Why]
This error message is unnecessary because returning when aconnector is
uninitialized is the desired outcome during initialization. As well, there
is no equivalent error message for read_dpcd.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>