net: uclass: Save generated ethernet MAC addresses to the environment

net: uclass: Save generated ethernet MAC addresses to the environment

When a MAC address is randomly generated we currently only update the
appropriate data structure.  For consistency and to re-align with
historic usage, it should be also saved to the appropriate environment
variable as well.

Cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
[trini: Update Kconfig, handle legacy networking case as well]
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Ramon Fried <rfried.dev@gmail.com>
Link: https://lore.kernel.org/r/1a2518e3cc19c14a41875ef64c5acc1f16edc813.1641893287.git.michal.simek@xilinx.com