mfd: qcom-i2c-pmic: Handle interrupt while suspended

The i2c controller device once suspended fails all the
i2c transactions. There is a possibility that an slave i2c
interrupt occurs while the device is suspended and the
interrupt callback does the i2c transactions before the controller
has resumed.

Handle this case by maintaining a suspend/resume flag and handle
the interrupt (i2c transactions) after the device has resumed.

CRs-Fixed: 2089695
Change-Id: Ib2fbf025db4a4e9722d915ba8dd49e901290260d
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>