ramips: fix up switch settings for Sitecom WL-351 v1 002

Pinmux for rgmii needs to be set to rgmii, not gpio.
Hide the ESW switch on boot (using new rgmii esw devicetree attribute).
Also add a Sitecom-specific profile, since the image needs to include
the rtl8366 kernel driver.

Signed-off-by: Tobias Diedrich <ranma+openwrt@tdiedrich.de>

ramips: move different subtarget image generation to separate makefiles to improve maintainability

- all subtarget specific defines are in their own files
- common defines left in main Makefile
- each subtarget makefile idefed with SUBTARGET
- all subtargets compile tested
- few seems to be broken/unneeded things marked with FIXME

Signed-off-by: Roman Yeryomin <roman@advem.lv>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@49104 3c298f89-4303-0410-b956-a3cf2f4a3e73