This change introduces support for wildcard patterns in "option path"
of section "wifi-device".

Objective is to allow paths like "*/usb[0-9]/*/*" in order to claim
any usb device using the same backend type, regardless of its bus
address or phy name.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

Backport of r41873

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@41965 3c298f89-4303-0410-b956-a3cf2f4a3e73