Introduce new low level init code for AR934x/QCA95xx and AR933x

Introduce new low level init code for AR934x/QCA95xx and AR933x

New code is simpler, more universal and supports:
- clock configuration stored in FLASH
- non-fractional PLL/clocks configuration
- recovery mode (sets safe clocks when recovery button is pressed)

This was tested on many different QC/A WiSoCs and platforms,
including new QCA95xx chips.

Code for AR933x still needs some additional work. The original code
from Atheros SDK is very buggy and includes lot of (still) unknown
parts, like "pmu setup", "meas", etc. It seems that most of that
is related with radio configuration.