ath10k: Get rid of "per_ce_irq" hw param

As of the patch ("ath10k: Keep track of which interrupts fired, don't
poll them") we now have no users of this hardware parameter.  Remove
it.

Suggested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200709082024.v2.2.I083faa4e62e69f863311c89ae5eb28ec5a229b70@changeid