selftests: ncdevmem: Move ncdevmem under drivers/net/hw

This is where all the tests that depend on the HW functionality live in
and this is where the automated test is gonna be added in the next
patch.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20241107181211.3934153-12-sdf@fomichev.me


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