Add support for the intergrated I2C controller on Netlogic
XLR/XLS MIPS SoC.

The changes are to add a new file i2c/buses/i2c-xlr.c, containing the
i2c bus implementation, and to update i2c/buses/{Kconfig,Makefile} to
add the CONFIG_I2C_XLR option.
Signed-off-by: NGanesan Ramalingam <ganesanr@netlogicmicro.com>
Signed-off-by: NJayachandran C <jayachandranc@netlogicmicro.com>
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>