VOP_IOCTL() can return errors such as ENOTTY, which are not listed as errnos for lseek(2)
on either the man page nor in POSIX.
The trivial patch maps all errnos not listed in the man page (and POSIX) to EINVAL, which
is listed. This is done mainly for the ENOTTY case, but serves as a "catch-all" for any other
non-standard errnos that might be returned by the VOP_IOCTL().