Clock configuration will be needed by other/future subsystems such as i2c.
Extract the functionality from libgpio and put it into it's own library.
Change-Id: I6f6de0b3fb4d305ddfeac74123b78c983d1318dd
* Generalize GPIO handling.
* Add libs to configure gpio's clocks and pads
* Add Interrupt handling.
* Introduce mmio.h and log.h
Change-Id: I928e4c807d15031de2eede4b3ecff62df795f8ac