lantiq: Add support for the BT Home Hub 5A

u-boot support depends on the next "upstream" version ([0]) from
Daniel Schwierzeck.
Since the installation process is quite complicated a "how to" was
added to the wiki: [1]

[0] https://github.com/danielschwierzeck/u-boot-lantiq/tree/openwrt/v2014.01-next
[1] http://wiki.openwrt.org/toh/bt/homehub_v5a

V2: Use the correct PCI interrupt (fixes 2.4GHz wifi)
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
SVN-Revision: 46223