[astro][pll] Set SYS PLL rate before enabling it

Test: Boot up on astro, and "clkctl measure"

Change-Id: I01c45eb65cf466cd0fdf60ed0d196e34cabb3a45

[astro-thermal] Astro CPU freq. set to MAX 1.893GHz

- Added initial hooks for thermal notifications.
- Using CPU freq. scaling to setup boot up freq. to be
1.893 GHz.
- A couple of small bugs in Voltage regulator code.

ZX-2498 #done
ZX-2507 #done

Test: Validated CPU freq. using clkctl utility.

Change-Id: Ib38372e90c19efe2cefdf78627f024809668a0fb

[amlogic][cpu-freq] Add CPU Freq. Scaling support

- Added support for configuring the dynamic mux
to generate frequencies less than 1GHz using MPLL.
- Cleanup and bug fixes in HIU PLL library.

Test: Used clkctl utility to verfiy freq. changes are
actually applied.

Change-Id: I9ef0da66c73b15814b566e5ab07a565ac08b875a

[amlogic-clk] Enable certain clocks to allow measuring of CPU freq

- Enable CLK_SYS_PLL_DIV16 & CLK_SYS_CPU_CLK_DIV16 so we can
measure the actual CPU core freq.
- Enable clock gating for G12A family
- Currently added only support to enable/disable SYS_CPU clock
gates.
- Use Clock Protocol to enable these clocks.

Test: Manual testing on Astro.

Change-Id: I52f16aca885e8e8566337204f9b1dbd8ba281993