The new PRIV_VMM_CREATE and DESTROY permissions should be allowed by
jails, so need to be added to the list in prison_priv_check(). Then,
modify vmmdev_create() to verify that the jail was created with the
allow.vmm flag.
Rename vmm_priv_check() to vmm_jail_priv_check() to make the function's
purpose more clear.
Reported by: novel
Fixes: d4c05edd410e ("vmm: Add privilege checks to vmmctl operations")