[boot] uboot-lantiq: change package src to tarball/patch and update to v2013.01-rc2

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
[boot] uboot-lantiq: add support for Lantiq EASY50712 eval board

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
[boot] uboot-lantiq: add support for Lantiq EASY80920 eval board

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>