net: dsa: qca8k: Fix spelling mistake "Mismateched" -> "Mismatched"

There is a spelling mistake in a netdev_err error message. Fix it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20211125002932.49217-1-colin.i.king@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>