usbnet: modern method to get random MAC

The driver generates a random MAC once on load
and uses it over and over, including on two devices
needing a random MAC at the same time.

Jakub suggested revamping the driver to the modern
API for setting a random MAC rather than fixing
the old stuff.

The bug is as old as the driver.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Link: https://patch.msgid.link/20240829175201.670718-1-oneukum@suse.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>