If we have a per CE (Copy Engine) IRQ then we have no summary
register.  Right now the code generates a summary register by
iterating over all copy engines and seeing if they have an interrupt
pending.

This has a problem.  Specifically if _none_ if the Copy Engines have
an interrupt pending then they might go into low power mode and
reading from their address space will cause a full system crash.  This
was seen to happen when two interrupts went off at nearly the same
time.  Both were handled by a single call of ath10k_snoc_napi_poll()
but, because there were two interrupts handled and thus two calls to
napi_schedule() there was still a second call to
ath10k_snoc_napi_poll() which ran with no interrupts pending.

Instead of iterating over all the copy engines, let's just keep track
of the IRQs that fire.  Then we can effectively generate our own
summary without ever needing to read the Copy Engines.

Tested-on: WCN3990 SNOC WLAN.HL.3.2.2-00490-QCAHLSWMTPL-1
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rakesh Pillai <pillair@codeaurora.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200709082024.v2.1.I4d2f85ffa06f38532631e864a3125691ef5ffe06@changeid