drm/amd/powerplay: change sysfs pp_dpm_xxx format for navi10

v2:
set average clock value on level 1 when current clock equal
min or max clock (fine grained dpm support).

the navi10 gfxclk (sclk) support fine grained DPM,
so use level 1 to show current dpm freq in sysfs pp_dpm_xxx

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>