drm/amd/display/dc: set num-dwb = 1 as navi10 asic cap

during navi10 bring up, dwb causes system hang.
to continue debug major issue, disable dwb by
set num-dwb = 0. the hang issue is not reproduced now
by enable num-dwb =1. dc source is shared by all os.
win needs num-dwb = 1.

Signed-off-by: hersen wu <hersenxs.wu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>