wifi: ath9k: fix kernel-doc warnings in common-debug.h

wifi: ath9k: fix kernel-doc warnings in common-debug.h

Modify kernel-doc comments in common-debug.h to avoid warnings:

Warning: drivers/net/wireless/ath/ath9k/common-debug.h:21 bad line:
  may have had errors.
Warning: ../drivers/net/wireless/ath/ath9k/common-debug.h:23 bad line:
  may have had errors.
Warning: ../drivers/net/wireless/ath/ath9k/common-debug.h:26 bad line:
  decryption process completed
Warning: ../drivers/net/wireless/ath/ath9k/common-debug.h:28 bad line:
  encountered an error

Fixes: 99c15bf575b1 ("ath9k: Report total tx/rx bytes and packets in debugfs.")
Fixes: 1395d3f00a41 ("ath9k: Add debugfs file for RX errors")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://patch.msgid.link/20251117020251.447692-1-rdunlap@infradead.org
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>