cw1200: replace a set of atomic_add()

a set of atomic_inc() looks more readable

Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1604991491-27908-1-git-send-email-yejune.deng@gmail.com