msm: kgsl: Clear pending GMU IRQs before enabling

The mask register for GMU IRQs defaults to all bits on.
This could lead to pending invalid interrupts that would come
through when the interrupts are enabled on the host side.
Factor out the IRQ enabling and disabling code to make
it cleaner and clear pending IRQs before enabling them.

Additionally, add the HFI_IRQ_CM3_FAULT_MASK interrupt
mask and factor out the IRQ handlers and probe.

CRs-Fixed: 2017390
Change-Id: Iab7a3a8b76d493c016977fda03c7cd9f54166086
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>