Fix the below warning as the core looks for the compatible
string.

[    5.198919] i2c i2c-18: of_i2c: modalias failure on
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@19
[    5.207454] i2c i2c-18: Failed to create I2C device for
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@19
[    5.216394] i2c i2c-18: of_i2c: modalias failure on
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@30
[    5.224986] i2c i2c-18: Failed to create I2C device for
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@30
[    5.233927] i2c i2c-18: of_i2c: modalias failure on
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@35
[    5.242527] i2c i2c-18: Failed to create I2C device for
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@35
[    5.263880] i2c i2c-18: of_i2c: modalias failure on
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@36
[    5.272477] i2c i2c-18: Failed to create I2C device for
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@36
[    5.281415] i2c i2c-18: of_i2c: modalias failure on
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@51
[    5.290008] i2c i2c-18: Failed to create I2C device for
/amba/i2c@ff030000/i2c-mux@75/i2c@3/dev@51

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>