drm/i915/alpm: Make intel_alpm_enable_sink available for PSR

drm/i915/alpm: Make intel_alpm_enable_sink available for PSR

We want to enable sink ALPM from PSR code. Make intel_alpm_enable_sink
available for PSR.

v2: do not add kerneldoc comments

Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/20250513054814.3702977-2-jouni.hogander@intel.com
(cherry picked from commit 2d278488761f0b5be651a3db41e615a964123d6c)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>