drm/amd/pm: fix pp_dpm_fclk

fclk value is missing in pp_dpm_fclk. add this to correctly show the current value.

Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 5.9.x