Add proper workaround for 3COM 3C90xB cards, which need special fixups (the 3C90xC ones don't)

This is tested on hardware.

Also, add initial support for the Atmel AT29C010A chip (which I inserted
in a 3COM 3C90xB card for testing). It can be detected, read works,
erase works, but write will need some additional code (will post in
another patch later).

Corresponding to flashrom svn r520.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>