spmi: pmic_arb: remove disabling of ACC bit

The interrupt controller code in the arbiter disables
the peripheral accumulated interrupt (ACC) bit when none of the
interrupts in the peripheral is enabled.

This is not required since the controller disables the interrupt
at the pmic.

So leave the ACC bit enabled while masking an interrupt. Also
ensure that the ACC bit is enabled while unmasking an interrupt.
There is no issues with enabling ACC bit if it were already enabled.

Change-Id: Idbea562157e65a4dfe0c51b7a25eed5ce000068d
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
[collinsd: fix merge conflict]
Signed-off-by: David Collins <collinsd@codeaurora.org>