MAINTAINERS: wifi: ath: add Jeff Johnson as maintainer

The "ATHEROS ATH GENERIC UTILITIES" entry shares the same git tree as
the ATH10K, ATH11K, and ATH12K entries which I already maintain, so
add me to that entry as well.

Signed-off-by: Jeff Johnson <jjohnson@kernel.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20241212-ath-maintainer-v1-1-7ea5e86780a8@kernel.org

Author: Jeff Johnson

MAINTAINERS

@@ -3608,6 +3608,7 @@ F:	drivers/phy/qualcomm/phy-ath79-usb.c
 
 ATHEROS ATH GENERIC UTILITIES
 M:	Kalle Valo <kvalo@kernel.org>
+M:	Jeff Johnson <jjohnson@kernel.org>
 L:	linux-wireless@vger.kernel.org
 S:	Supported
 F:	drivers/net/wireless/ath/*