spmi: pmic-arb: do not ack and clear peripheral interrupts in cleanup_irq

Currently, cleanup_irq() is invoked when a peripheral's interrupt
fires and there is no mapping present in the interrupt domain of
spmi interrupt controller.

The cleanup_irq clears the arbiter bit, clears the pmic interrupt
and disables it at the pmic in that order. The last disable in
cleanup_irq races with request_irq() in that it stomps over the
enable issued by request_irq. Fix this by not writing to the pmic
in cleanup_irq. The latched bit will be left set in the pmic,
which will not send us more interrupts even if the enable bit
stays enabled.

When a client wants to request an interrupt, use the activate
callback on the irq_domain to clear latched bit. This ensures
that the latched, if set due to the above changes in cleanup_irq
or when the bootloader leaves it set, gets cleaned up, paving way
for upcoming interrupts to trigger.

With this, there is a possibility of unwanted triggering of
interrupt right after the latched bit is cleared - the interrupt
may be left enabled too. To avoid that, clear the enable first
followed by clearing the latched bit in the activate callback.

Change-Id: If126d6f6cdf6c944ca513c53a71a91e225ee63e2
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>
[collinsd: fix merge conflict]
Signed-off-by: David Collins <collinsd@codeaurora.org>