ath79: port HiWiFi HC6361 from ar71xx

ath79: port HiWiFi HC6361 from ar71xx

The device was added for ar71xx target and dropped during the ath79
transition, mainly because of the ascii mac address stored in bdinfo
partition

Device page, http://wiki.openwrt.org/toh/hiwifi/hc6361

The vendor u-boot image accepts sysupgrade.bin image with specific
requirements, including having squashfs signature "hsqs" at file offset
0x140000.  This is not possible now that OpenWrt kernel image is at
least 2MB with the signature at offset 0x240000.

Installation of current build of OpenWrt now requires a bootstrap step
of installing an earlier version first.

 - If the vendor u-boot accepts sysupgrade image, hc6361 image of LEDE
   release should work
 - If the vendor u-boot accepts only verified flashsmt image, install
   the one in the above device page.  The image is based on Barrier
   Breaker

   SHA256SUM of the flashsmt image

	81b193b95ea5f8e5c30cd62fa9facf275f39233be4fdeed7038f3deed2736156

After the bootstrap step, current build of OpenWrt can be installed
there fine.

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>