drm/amd/pm: add GFXCLK/SCLK clocks level print support for APUs

add support that allow the userspace tool like RGP to get the GFX clock
value at runtime, the fix follow the old way to show the min/current/max
clocks level for compatible consideration.

=== Test ===
$ cat /sys/class/drm/card0/device/pp_dpm_sclk
0: 200Mhz *
1: 1100Mhz
2: 1600Mhz

then run stress test on one APU system.
$ cat /sys/class/drm/card0/device/pp_dpm_sclk
0: 200Mhz
1: 1040Mhz *
2: 1600Mhz

The current GFXCLK value is updated at runtime.

BugLink: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5260


Reviewed-by: Huang Ray <Ray.Huang@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org