drm/amd/pm: fix issue of missing '*' on pp_dpm_xxx nodes

drm/amd/pm: fix issue of missing '*' on pp_dpm_xxx nodes

refine the code to fix '*' missing on pp_dpm_xxx series node.

e.g.: missing '*' on navi10 pp_dpm_sclk
$ cat /sys/class/drm/card0/device/pp_dpm_sclk
0: 300Mhz
1: 1930Mhz (missing symbol '*')

Fixes: a08ea4bc7711 ("drm/amd/pm: Add a helper to show dpm table")
Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>