drm/amd/display: Add hubp clock status in DTN log for Navi

[Why]
For debug purpose, we need to check HUBP_CLOCK_ENABLE in DTN
log debugfs on Navi.

[How]
Add related register read in dcn20_hubp.c.

Signed-off-by: Leo (Hanghong) Ma <hanghong.ma@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>