ramips: TEW-692GR.dts fixes

* fix pinmux settings
* remove spi node
* add PCI node
* add nor-flash node

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36268 3c298f89-4303-0410-b956-a3cf2f4a3e73