sys/sys/vnode.h: Hide 'standard' VOP helper casts behind macros

Rather than having type-casted function pointers for rather
standard helper functions, provide some useful macro names that
are easy to remember. Re-factor with these names in mind.

The following are provided:

 VOP_NULL         ->  ((void*)(uintptr_t)vop_null)
 VOP_EBADF        ->  ((void*)(uintptr_t)vop_ebadf)
 VOP_ENOTTY       ->  ((void*)(uintptr_t)vop_enotty)
 VOP_EINVAL       ->  ((void*)(uintptr_t)vop_einval)
 VOP_EOPNOTSUPP   ->  ((void*)(uintptr_t)vop_eopnotsupp)

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/sys/vnode.h: Introduce VOP_PANIC macro for bad VOP's

We later make use of this to reduce some repetition of a
common helper VNOP function that panic's the system on
'bad' VOP's.

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/vfs/ufs/ufs_vnops.c: Convert to use VOP_PANIC macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/vfs/portal/portal_vnops.c: Convert to use VOP_PANIC macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/vfs/deadfs/dead_vnops.c: Convert to use VOP_PANIC macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/vfs/fifofs/fifo_vnops.c: Convert to use VOP_PANIC macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/sys/vnode.h: Introduce VOP_EIO macro for I/O errno in VOPs

We later make use of this to reduce some repetition of a
common helper VNOP function that return input/output error (EIO)
on 'bad' VOP's. As is defined in 'sys/sys/errno.h'.

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
linprocfs_vnops.c: Convert to use VOP_EIO macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
procfs/procfs_vnops.c: Convert to use VOP_EIO macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
devfs/devfs_vnop.c: Convert to use VOP_EIO macro

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/vfs/smbfs: Strip out vm_zone code from smbfs_vfsops.c

zone(9) has been depricated where the objcache(9) slab allocator
should be used in place. Here smbfs had already been converted,
however the previous dead implementation of vm_zone was left behind
so tear it out.

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>