net: devmem: don't call queue stop / start when the interface is down

We seem to be missing a netif_running() check from the devmem
installation path. Starting a queue on a stopped device makes
no sense. We still want to be able to allocate the memory, just
to test that the device is indeed setting up the page pools
in a memory provider compatible way.

This is not a bug fix, because existing drivers check if
the interface is down as part of the ops. But new drivers
shouldn't have to do this, as long as they can correctly
alloc/free while down.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250206225638.1387810-3-kuba@kernel.org


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