generic: ar8216: move PHY4 RGMII workaround code out of the loop

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35603 3c298f89-4303-0410-b956-a3cf2f4a3e73