ipq806x: add db149 dts files

DB149 is an IPQ806x based development platform. This patch adds the dts
files to support it.

Signed-off-by: Mathieu Olivari <mathieu@codeaurora.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45536 3c298f89-4303-0410-b956-a3cf2f4a3e73