drivers: hwinfo: rpi_pico: use bootrom method on RP2350

RP2350 provides a function to get OTP-backed chip ID. Prefer using this
on supported platforms for these reasons:
- a secure internal identifier, same as read by picotool
- works on flashless boards
- does not conflict with code running in XIP mode (e.g. when the other
 core tries to access device ID)
- when used with USB HWID serial number will match one BootROM has

Signed-off-by: Dmitrii Sharshakov <d3dx12.xx@gmail.com>
Co-authored-by: Alexander Wachter <alexander@wachter.cloud>