EPG5000 uses ath79 nvram functions, but does not select it. This breaks
build if no other board support enabling nvram support is selected.

Closes #19952.

Backport of r46190.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>


git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@46494 3c298f89-4303-0410-b956-a3cf2f4a3e73