LU-14776 zfs: fix Ubuntu 20 HWE build issues

LU-14776 zfs: fix Ubuntu 20 HWE build issues

With newer Ubuntu systems using ZFS dkms have the following build
errors:

    In file included from zfs/2.0.2/source/include/sys/arc.h:32,
                 from lustre/osd-zfs/osd_internal.h:50,
                 from lustre/osd-zfs/osd_handler.c:51:
    zfs/2.0.2/source/include/sys/zfs_context.h:45:10:
                 fatal error: sys/types.h: No such file or directory
    45 | #include <sys/types.h>
       |          ^~~~~~~~~~~~~
    compilation terminated.

This is due to layout of the tree containing the needed headers.
Include those paths in build system.

Test-Parameters: trivial
Change-Id: I453830c4111ad88ec655d3d7d0ee51627331cb0b
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/44749
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>