i2c: iproc: Change driver to use 'BIT' macro

Change the iProc I2C driver to use the 'BIT' macro from all '1 << XXX'
bit operations to get rid of compiler warning and improve readability of
the code

Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>