drm/i915/dp: Read ALPM caps after DPCD init

drm/i915/dp: Read ALPM caps after DPCD init

For eDP read the ALPM DPCD caps after DPCD initalization and just before
the PSR init.

v2: Move intel_alpm_init to intel_edp_init_dpcd (Jouni)
v3: Add Fixes with commit-id (Jouni)
v4: Separated the alpm dpcd read caps from alpm_init and moved to
intel_edp_init_dpcd.
v5: Read alpm_caps always for eDP irrespective of the eDP version (Jouni)
v6: replace drm_dp_dpcd_readb with drm_dp_dpcd_read_byte (Jouni)

Fixes: 15438b325987 ("drm/i915/alpm: Add compute config for lobf")
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patch.msgid.link/20260304072157.1123283-1-arun.r.murthy@intel.com
(cherry picked from commit 88442ba208dd5d3405de3f5000cf5b2c86876ae3)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>