drm/i915/dmc: Add interface to block PKG C-state

Add interface to block PKG C-state. This is needed to implement workaround
for underrun on idle PSR HW issue (Wa_16025596647).

Bspec: 74151
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://lore.kernel.org/r/20250414100508.1208774-6-jouni.hogander@intel.com