ar71xx: add kernel support for the EnGenius ESR900

Signed-off-by: Forest Crossman <cyrozap@gmail.com>
Patchwork: http://patchwork.openwrt.org/patch/5714/


[juhosg:
  - drop nvram.c modifications,
  - create a separate kernel patch,
  - use ath79_setup_qca955x_eth_cfg helper,
  - merge esr900_{010,common}_setup functions,
  - statically init AR8327 pad configurations,
  - use pr_err instead of printk]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 41640