ar71xx: configure OBS4 line on TL-WR841N-v8/MR3420v2

It also fixes USB Power on MR3420v2.

This time we took the information from the source of GPL:
http://www.mail-archive.com/openwrt-devel@lists.openwrt.org/msg18970.html
Confirmed and tested:
https://dev.openwrt.org/ticket/13201#comment:41
Thanks to oguretsagressive for testing.

Signed-off-by: Dmytro <dioptimizer@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37878 3c298f89-4303-0410-b956-a3cf2f4a3e73
ar71xx: image: dynamically generate Image/Build/Template/* macros

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37879 3c298f89-4303-0410-b956-a3cf2f4a3e73
generic: remove linux version checks from myloader.c

The myloader partition parser code uses ifdef wrappers
to make the code usable on kernels below version 3.2.
All targets are using kernel 3.3 at least so the wraper
is not needed. Remove that.

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37880 3c298f89-4303-0410-b956-a3cf2f4a3e73