[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

[astro][voltage] Add Voltage Scaling support

Added interface to get/set voltage using the PWM
This will be later used for DVFS

Test: boot up on Astro
Change-Id: I9fc6b70af399b0ac9d0bb90034f0bfd1b94c5d5d

[astro][pwm] Add PWM driver for voltage scaling

Adding a PWM driver which would allow to set duty cycle
for a particular PWM

Test: Verified duty cycle on scope for PWM_D

Change-Id: I03cd8242674d4320dd973a7cb0167598475de5c1

[astro][thermal] Initial commit for Temp Sensor

This CL is first of many to follow.
Thermal driver for Astro implements the following:
- Adds a thermal driver
- Thermal driver will consist of following:
- Temperature Sensor driver
- CPU Voltage & Frequency Scaling driver
- Some logic to set trip points etc.

This CL focuses primarily on the Temperature Sensor

Test: Tested on Astro and verified reading correct temp

Change-Id: I041c237389becd9876a6f0693e3d1248a2c83447