wext: Add support for renamed Host AP driver ifname

wext: Add support for renamed Host AP driver ifname

Previous workaround for WEXT events from the Host AP driver required
wlan# and wifi# interfaces to have fixed names with the same number.
While that used to be the common case ten years ago, it is less common
nowadays. Extend this to use sysfs (if available) to figure out the
wifi# interface name if the specified interface is detected to be using
the Host AP driver.

Signed-off-by: Jouni Malinen <j@w1.fi>