Retire HAVE_IOCTL_* configure checks

The HAVE_IOCTL_* configure checks were originally added for
compatibility with an ancient version of glibc. This support
and additional complexity is no longer needed and is therefore
being removed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Closes #585