kni: increase kernel version requirement for VA

kni: increase kernel version requirement for VA

A build error reported related to the selected 'get_user_pages_remote()'
kernel API:

.../kernel/linux/kni/kni_dev.h:113:8:
  error: too few arguments to function ‘get_user_pages_remote’
  ret = get_user_pages_remote(tsk, tsk->mm, iova, 1
        ^~~~~~~~~~~~~~~~~~~~~

Currently there are three versions of the 'get_user_pages_remote()'
supported, based on kernel version < 4.9, = 4.9, > 4.9.

These version based checks are not working fine with the distro kernels
which is the cause of reported build error. The error reported by the
kernel version 4.8, but it is using API defined in > 4.9.

To be able to take control of this, and possible more, related build
error, increasing the minimum supported kernel version for iova=va with
KNI to kernel version 4.9.

This leaves us with single version of the kernel API and more manageable.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>