perf tests test_bridge_fdb_stress.sh: Fix redirection of stderr to stdin

It's not 2&>1, the correct is 2>&1.

Signed-off-by: Patrice Duroux <patrice.duroux@gmail.com>
Cc: linux-kselftest@vger.kernel.org
Link: https://lore.kernel.org/r/20230303193058.21274-1-patrice.duroux@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>