msm: iommu: Use threaded IRQ handler for page faults

A threaded interrupt handler for IOMMU page faults will
allow the use of the new clock APIs from the interrupt
handler.

Change-Id: I381df3974daa7fbc4bc4ec0558434959597b4f24
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>

Conflicts:
	arch/arm/mach-msm/iommu_dev.c