drm/amd/powerplay: fix bug that dpm funcs in debugfs/sysfs missing.

in dpm module, sysfs init func move to late_init from sw_init.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

Change-Id: Ice4a73212d8e3106d05f04a27043820ffd32929e
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>