This patch fixes build failing with undefined symbol _PAGE_IOMAP with
kernel 3.18.
The Xen-specific _PAGE_IOMAP PTE flag was removed in kernel 3.18 and
could be used for other purpose in future. This patch ensures that
_PAGE_IOMAP flag is only used for kernels before 3.18.
Signed-off-by: Shu Shen <shu.shen@radisys.com>
Acked-by: Jincheng Miao <jmiao@redhat.com>
0d6e2d783d