tests/samples: net: Fix the max number of file descriptors Make sure that CONFIG_ZVFS_OPEN_MAX in the tests and samples is at least the same value as CONFIG_NET_SOCKETS_POLL_MAX so that we cannot have more polled sockets than there are available file descriptors. Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no> (cherry picked from commit 759f3a0c7c641e9af9d0aac3397abf687443d1a0)