i2c: msm-geni: I2C controller driver for GENI based serial engine.

This I2C controller driver implements an adapter and communicates with
Qualcomm Technologies Inc.'s GENI based I2C serial-engine.
At this time, FIFO mode is supported for all size transfers. The
transfers are executed synchronously and an interrupt indicates if
the transfer is complete. Watermark is used on TX and RX if the data
size is greater than FIFO size. In that case, intermittent interrupts
fill-in or consume the FIFO and the last interrupt signals completion.
In case of an error (e.g. timeout due to slaves holding lines low),
the serial-engine is restored to reset/idle state by executing
abort command.

Change-Id: I94aca3d269a45d9cab2b5e15f8e42b0d29739238
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>