drm/amd/display: Fully remove i2caux folder

This is a follow up to:
e28e1490794d ("drm/amd/display: Remove i2caux folder")

Some files were still left, so delete all of them.

CC: David Francis <David.Francis@amd.com>
CC: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>