I2C driver initialization must consider if the pin was defined as I2C

If a board doesn't use all I2C buses, then the I2C module should not try to handle/config all the possible I2C modules in its driver.

A simple solution would be to add a `#ifdef` guard in `port/board/ucontroller/nxp/lpc17_i2c.c` where it tries to access `I2CX_SCL` and `I2CX_SDA` pins definitions.