FreeBSD: Parameterize ZFS_ENTER/ZFS_VERIFY_VP with an error code

For legacy reasons, a couple of VOPs have to return error numbers that
don't come from the usual errno namespace. To handle the cases where
ZFS_ENTER or ZFS_VERIFY_ZP fail, we need to be able to override the
default error return value of EIO. Extend the macros to permit this.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes #13311