drm/amd/pp: Simplified the avfs btc state on smu7

AVFS feature support/not support is enough to driver.

so remove the complex define of the avfs btc state.

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>