ath10k: ath10k_snoc_{read,write}32() should be static

They're provided as callbacks in ath10k_hif_ops and should be accessed
that way, if needed outside of snoc.c, and anyway, they're currently
unused outside snoc.c.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>