libertas_tf: Fix wrong function name in comments

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/marvell/libertas_tf/if_usb.c:56: warning: expecting prototype for if_usb_wrike_bulk_callback(). Prototype was for if_usb_write_bulk_callback() instead

Signed-off-by: Yang Shen <shenyang39@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210517050141.61488-8-shenyang39@huawei.com