ath10k: make some functions static

Fixes the following sparse warnings:

drivers/net/wireless/ath/ath10k/snoc.c:823:5: warning:
 symbol 'ath10k_snoc_get_ce_id_from_irq' was not declared. Should it be static?
drivers/net/wireless/ath/ath10k/snoc.c:871:6: warning:
 symbol 'ath10k_snoc_init_napi' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>