msm_sensor_spi: SPI driver for reading from sensor EEPROM

For a new camera sensor we are working on, an EEPROM is used to hold
sensor specific data, including calibration data.  SPI is the only
interface to read EEPROM data.  This patch provides sensor drivers with
an SPI interface similar to current I2C framework.

Change-Id: Ibf60c3607a7c9c00871b5c934b500985ba6d98c8
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>