Add sysctl driver for K210 SoC providing clock and reset control:
- Clock enable/disable with two-stage APB/peripheral enable pattern
- Peripheral reset control with proper timing
- Clock frequency query for PLL, CPU, APB buses, and peripherals
- PLL frequency calculation and CPU frequency configuration
The sysctl driver is built unconditionally for K210 boards as it
provides essential clock and reset control functionality.
Add Kconfig option:
- K210_CPU_FREQ: Target CPU frequency in Hz (default 400MHz)
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>