staging: r8188eu: fall back to random mac address

Call eth_random_addr to generate a random mac address if we cannot load
the mac address from the efuses.

Do not use a constant mac address as fallback. This may create conflicts
if we have several r8188eu devices on the network.

Suggested-by: Joe Perches <joe@perches.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Reviewed-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220713075552.140927-1-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>