ramips: rt305x: add support for Accton WR6202 / SMCWBR11S-3GN

ramips: rt305x: add support for Accton WR6202 / SMCWBR11S-3GN

This patch adds support for the Accton WR6202 Mini 3G broadband router.
Full details for this device are available at
http://www.awbnetworks.com/products03.php?Fullkey=19.

This device is identical to the SMCWBR11S-3GN:
http://www.smc-asia.com/products03.php?Fullkey=210

It's also worth noting that this board has a GPIO line to control the
power to the USB port.

[juhosg:
 - fix checkpatch warnings,
 - reorder Kconfig entry,
 - merge the sysupgrade patch,
 - add GPL header]

Signed-off-by: Johnathan Boyce <jon.boyce@globalreach.eu.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@30434 3c298f89-4303-0410-b956-a3cf2f4a3e73