drm/amd/display: Remove the unused function copy_stream_update_to_stream()

drm/amd/display: Remove the unused function copy_stream_update_to_stream()

The function copy_stream_update_to_stream() is defined in the notif.c
file, but not called elsewhere, so delete this unused function.

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:2852:6: warning: no previous prototype for ‘dc_reset_state’.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2113
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>