net: remove aurora nb8800 driver

The tango4 platform is getting removed, and this driver has no
other known users, so it can be removed.

Cc: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Mans Rullgard <mans@mansr.com>
Link: https://lore.kernel.org/r/20210120150703.1629527-1-arnd@kernel.org


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