ANDROID: sched/walt: Accounting for number of irqs pending on each core

Schedules on a core whose irq count is less than a threshold.
Improves I/O performance of EAS.

Change-Id: I08ff7dd0d22502a0106fc636b1af2e6fe9e758b5
Signed-off-by: Andres Oportus <andresoportus@google.com>