wifi: iwlwifi: mvm: avoid outdated reorder buffer head_sn

wifi: iwlwifi: mvm: avoid outdated reorder buffer head_sn

If no frames are received on a queue for a while, the reorder buffer
head_sn may be an old one. When the next frame that is received on
that queue and buffered is a subframe of an AMSDU but not the last
subframe, it will not update the buffer's head_sn. When the frame
release notification arrives, it will not release the buffered frame
because it will look like the notification's NSSN is lower than the
buffer's head_sn (because of a wraparound).
Fix it by updating the head_sn when the first frame is buffered.

Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Reviewed-by: Daniel Gabay <daniel.gabay@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250723094230.795ec0cb8817.I9ec9a3508e7935e8d1833ea3e086066fdefee644@changeid