When synthesizing mmap events, add MAP_HUGETLB map flag if the source of
mapping is file in hugetlbfs.

After this patch, perf can identify hugetlb mapping even if perf is
started after the mapping of huge pages (like with 'perf top').
Signed-off-by: NWang Nan <wangnan0@huawei.com>
Reviewed-by: NNilay Vaish <nilayvaish@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Hou Pengyang <houpengyang@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1473137909-142064-4-git-send-email-wangnan0@huawei.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>