flashrom: Fix wrong VT8235 flash enable failed warning.
* Fix harmless but worrying warning where the return value of
pci_write_byte is misinterpreted.
* Hash together VT8231 and VT8235 code into VT823x. VT8231 is the better
implementation, but lacked the write protect disable code that's
apparently needed for VT8235.
Signed-off-by: Luc Verhaegen <firstname.lastname@example.org>
Signed-off-by: Uwe Hermann <email@example.com>
Acked-by: Stefan Reinauer <firstname.lastname@example.org>