net: ibm: emac: mal: fix potential system hang in mal_remove()

net: ibm: emac: mal: fix potential system hang in mal_remove()

napi_disable() is not idempotent and calling it on an already-disabled
or unenabled NAPI context will cause the kernel to spin indefinitely
waiting for the NAPI_STATE_SCHED bit to clear.

In mal_remove(), napi_disable() is called unconditionally. If no MACs were
registered, NAPI was never enabled. Also, if they were registered but
subsequently unregistered, NAPI was already disabled in
mal_unregister_commac(). In either case, calling napi_disable() causes
the kernel to hang upon module removal.

Fix this by only calling napi_disable() in mal_remove() if the commac list
is not empty (which implies NAPI is enabled).

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://patch.msgid.link/20260603230821.5619-1-rosenp@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>