generic: ar8216: add AR8337N switch support

generic: ar8216: add AR8337N switch support

This patch is needed to use the switch inside the Sitecom WLR-8100;
it was unusable and detected as Generic-Phy before.

since ar8337 is behaving like ar8327
generally do the same thing
see: https://forum.openwrt.org/viewtopic.php?pid=214218#p214218
forward-ported to trunk

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
Patchwork: http://patchwork.openwrt.org/patch/4469/
[juhosg: merge chip_is_ar83[23]7 statements in ar8xxx_phy_config_init]
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
SVN-Revision: 38952