Add support for AST2400 Super I/O.
The device doesn't have an ID register, so probe for scratch register
not to read as 0xff.
Tested on platform which has an AST2400.
Change-Id: I86af69c6b2ccefe2c88eef875bc858239df834f1
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32984
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Patrick Rudolph