PM / devfreq: bimc-bwmon: Use free_irq during governor suspend/stop

Use free_irq to free the interrupt handler for a shared interrupt.

Enable_irqs are not refcounted, whereas disable_irqs are. Depth variable
in irq_desc is actually disable-depth, for nested irq_disable() calls.
It can have value from 0 to N. 0 is when interrupt is enabled and N shows
the irq_disable depth.

Lets say, if  disable_irq is called 4 times, driver need to call
enable_irq 4 times to actually enable the interrupt back. But if
enable_irq is called 4 times, only one disable_irq needed to actually
disable the interrupt.

Use request/free_irq instead of disable/enable_irq.

Change-Id: Ie7fe866b403da9bf363f741b1693361b8e2f6a3d
Signed-off-by: Arun KS <arunks@codeaurora.org>