ARM: configs: remove oxnas_v6_defconfig

Due to lack of maintainance and stall of development for a few years now,
and since no new features will ever be added upstream, remove support
for OX820 specific defconfig.

Acked-by: Linus Walleij <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Acked-by: Daniel Golle <[email protected]>
Signed-off-by: Neil Armstrong <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>

Author: superna9999