DT: MIPS: ralink: clean up RT3050 dtsi and dts file

* remove nodes for cores whose drivers are not upstream yet
* add compat string for an additional soc
* fix a whitespace error

Signed-off-by: John Crispin <blogic@openwrt.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Patchwork: http://patchwork.linux-mips.org/patch/5186/