i2c-ssbi: Add SSBI driver for 7x30

Initial implementation of the MSM SSBI driver.

The MSM SSBI driver uses the i2c framework rather than implement its own
core driver. The i2c framework was chosen over w1 or spi because these
drivers do not support a mechanism for passing in a slave device register
address which is required by the SSBI protocol. Rather than prepending
the register address to the user data, the i2c driver is used by
overloading the slave device address to be used as the device register
address.

Signed-off-by: Kenneth Heitke <kheitke@quicinc.com>