hw/arm/npcm7xx: add board setup stub for CPU and UART clocks

hw/arm/npcm7xx: add board setup stub for CPU and UART clocks

When booting directly into a kernel, bypassing the boot loader, the CPU and
UART clocks are not set up correctly. This makes the system appear very
slow, and causes the initrd boot test to fail when optimization is off.

The UART clock must run at 24 MHz. The default 25 MHz reference clock
cannot achieve this, so switch to PLL2/2 @ 480 MHz, which works
perfectly with the default /20 divider.

The CPU clock should run at 800 MHz, so switch it to PLL1/2. PLL1 runs
at 800 MHz by default, so we need to double the feedback divider as well
to make it run at 1600 MHz (so PLL1/2 runs at 800 MHz).

We don't bother checking for PLL lock because we know our emulated PLLs
lock instantly.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
Message-id: 20200911052101.2602693-13-hskinnemoen@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>