ao-tools: Clean up ao-stmload and ao-usbload options. Add --raw

ao-stmload only uses stlink, ao-usbload only uses self-flashing, so
clear up the options in the two programs. The new --raw option skips
the serial and radio cal rewriting when flashing the boot loader.

Signed-off-by: Keith Packard <keithp@keithp.com>