clk: Add support for I2C clocks on NXP's imx6q SoC which use CCF

This change adds support for I2C clock modeled in CCF. This code intention
is to only enable those clocks in the I2C driver with default settings.
For that reason the "busy" versions of clocks reuse the generic approach
and would need to be updated when one wants to adjust the I2C clock
frequency in U-Boot.

Signed-off-by: Lukasz Majewski <lukma@denx.de>