i2c: tegra: Fix i2c unknown interrupt issue

writes to modules on APB bus may complete out-of-order. need
to guarantee that the write is completed by reading it back.

read I2C_INT_STATUS back right after writing the current int status
in the isr to make sure the clear operation of I2C_INT_STATUS is
done before the interrupt is re-enabled.
the same also done for DVC_STATUS.

bug 980763

Change-Id: I34f18804d530ccadf561fe1736552b6a4dd6e4ce
Signed-off-by: Ken Chang <kenc@nvidia.com>
Reviewed-on: http://git-master/r/101925
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>