drm/amd/pm: add inst to dpm_set_vcn_enable

Add an instance parameter to the existing function dpm_set_vcn_enable()
for future implementation. Re-write all pptable functions accordingly.

v2: Remove duplicated dpm_set_vcn_enable() functions in v1. Instead,
adding instance parameter to existing functions.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>
Suggested-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>