drm/i915/alpm: Write PR_ALPM_CTL register

PR_ALPM_CTL register contains configurations related to Adaptive sync
sdp. Configure these if Adaptive Sync SDP is supported.

v2: avoid using hardcoded indices

Bspec: 71014
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://lore.kernel.org/r/20250526120512.1702815-6-jouni.hogander@intel.com