staging: ath6kl: remove-typedef AR6K_GMBOX_CTRL_REGISTERS

remove-typedef -s AR6K_GMBOX_CTRL_REGISTERS \
	"struct ar6k_gmbox_ctrl_registers" drivers/staging/ath6k

Cc: Naveen Singh <naveen.singh@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>