Avoid harmless error from network script by checking presence of
now-optional wifi support script, most notably confusing users of x86
snapshots.
Fixes: #14964
Signed-off-by: Andris PE <neandris@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/14986
Signed-off-by: Robert Marko <robimarko@gmail.com>
(cherry picked from commit 207bfee855)