drm/amd/display: Add otg_master NULL check within resource_log_pipe_topology_update

[Why]
Coverity reports NULL_RETURN warning.

[How]
Add otg_master NULL check.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>