afs: remove variable nr_servers

afs: remove variable nr_servers

[ Upstream commit 318b83b71242998814a570c3420c042ee6165fca ]

Variable nr_servers is no longer being used, the last reference
to it was removed in commit 45df8462730d ("afs: Fix server list handling")
so clean up the code by removing it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20221020173923.21342-1-colin.i.king@gmail.com/
Stable-dep-of: add117e48df4 ("afs: Fix the server_list to unuse a displaced server rather than putting it")
Signed-off-by: Sasha Levin <sashal@kernel.org>