[U-Boot] [PATCH V2] arm: timer and interrupt init rework

[Michael Roth]

Wolfgang Denk schrieb:

> What is "slow clock"?

On (some) ARM SoC there are two oscillators: A "slow" free running
oscillator typically with a dedicated 32 kHz crystal and the "main"
oscillator with a dedicated crystal in the MHz range.

The processor starts with the slow slock enabled and init code needs
to set up PLLs and muxes etc. to enable the main oscillator and switch
to derived clocks like master clock, cpu clock, IO clock and so on.