Detect AMD Yangtze (found in Kabini and Tamesh).

The PCI ID of the LPC bridge doesn't change between Hudson-2/3/4 and
Yangtze (Kabini/Temash) but the SPI interface does. Bail out in case we
detect Yangtze and add infrastructure to distinguish other families too for
further refactorings.

Also, add ASRock IMB-A180 to the laptop whitelist and refine the IMC
warning a bit.

Tested on ASRock IMB-A180 with and w/o USE_YANGTZE_HEURISTICS, and
by Chris Goodrich from Sage on
 - SB600
 - SB700
 - SB800
 - Hudson 3 (A70M)
 - Kabini

Signed-off-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>

git-svn-id: svn://coreboot.org/flashrom/trunk@1706 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1