net: qmi_wwan: prevent duplicate mac address on link (firmware bug workaround)

net: qmi_wwan: prevent duplicate mac address on link (firmware bug workaround)

[ Upstream commit cc6ba5fdaabea7a7b28de3ba1e0fe54d92232fe5 ]

We normally trust and use the CDC functional descriptors provided by a
number of devices.  But some of these will erroneously list the address
reserved for the device end of the link.  Attempting to use this on
both the device and host side will naturally not work.

Work around this bug by ignoring the functional descriptor and assign a
random address instead in this case.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>