Refactor clock tree code
PC99 chardev, IMX31 IPF_FREQ tweak, remove IMX cumulative timer.

This patch:
1. Adds chardev support for the COM1 - COM4 serial devices on
   x86, serial input / output & irqs are supported.
2. Tweaks iMX31 IPG_FREQ, seemed to be a factor of 10 or so off
   (don't know the real value for KZM so guesswork is involved
   here).
3. Removes accumulative timer feature on IMX devices, in order
   to be consistent with the rest of the timer_ interface
   implementations.

reviewed by: adanis, alyons, akroh
Exynos clocks: Generalise PLLs and Dividers
Exynos5 clock tree: Implement PLLs and fix register offsets for peric
Exynos Serial: merge exynos4 and exynos5 serial drivers
Serial drivers: Refactor source tree and support for apq8064
Serial: Import missing drivers from libsel4platsupport. They are #if ed out until they can be integrated and tested
x86 serial: Fix default COM port selection
Exynos5 serial: squash stray #error
Import TMU from AndiC
Exynos serial: Squash printfs in serial initialisation code to remove recursive on-demand initialisation
PC99 chardevice: Add EGA device
Exynos4 MUX: provide support for UART
Serial: Widdle parity enum and use correct enum when configuring sabre
Character device: Switch to asyc API. Implemented async model for Exynos5
Exynos: Provide function for initialising serial by providing a virtual address and fix initialisation of IRQs
Remove references to sel4 headers
Exynos serial: Clean up RX IRQ logic and act only on pending IRQs that are unmasked
Exynos clocks: Fix div configuration helper argument order
Exynos clock: SPI change priority in divider calibration to ensure that per-divider frequency limits are adhered to