drm/amd/pp: Add stable Pstate clk display support in debugfs

The additional output are: PSTATE_SCLK and PSTATE_MCLK value
in MHz as:

300 MHz (PSTATE_SCLK)
300 MHz (PSTATE_MCLK)

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>