PM / devfreq: cache_hwmon: Move IRQ handling to device drivers

The cache monitoring devices might have more than one IRQ to handle
or might have notifications from other drivers instead of using actual
IRQs. So, refactor the governor to move the IRQ handling to the cache
monitoring device specific drivers and just provide an API that can be
used to request a re-evaluation.

The device specific driver can call this API to request an immediate
re-evaluation whenever the cache request has exceeded the previously
set limit instead of waiting for the periodic update.

Change-Id: Ib2e9f53f95749d659f440739a1b074b5a0d94fd8
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>