wifi: ath9k: use unsigned long for activity check timestamp

wifi: ath9k: use unsigned long for activity check timestamp

Since 'rx_active_check_time' of 'struct ath_softc' is in jiffies,
prefer 'unsigned long' over 'u32' to avoid possible truncation in
'ath_hw_rx_inactive_check()'. Found with clang's -Wshorten-64-to-32,
compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://patch.msgid.link/20250115171750.259917-2-dmantipov@yandex.ru
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>