Currently in gsi_isr_ieob(), event ring IEOB interrupts are disabled
one at a time.  The loop disables the IEOB interrupt for all event
rings represented in the event mask.  Instead, just disable them all
at once.

Disable them all *before* clearing the interrupt condition.  This
guarantees we'll schedule NAPI for each event once, before another
IEOB interrupt could be signaled.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>