net: lan78xx: replace bogus endpoint lookup

[ Upstream commit ea060b35 ]

Drop the bogus endpoint-lookup helper which could end up accepting
interfaces based on endpoints belonging to unrelated altsettings.

Note that the returned bulk pipes and interrupt endpoint descriptor
were never actually used. Instead the bulk-endpoint numbers are
hardcoded to 1 and 2 (matching the specification), while the interrupt-
endpoint descriptor was assumed to be the third descriptor created by
USB core.

Try to bring some order to this by dropping the bogus lookup helper and
adding the missing endpoint sanity checks while keeping the interrupt-
descriptor assumption for now.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>