However it does not really check the entry to be a section mapping which it should.
Returning pmd_sect(READ_ONCE(*pmdp)) is the right thing, which should have been the
case from the beginning when vmemmap_check_pmd() was added. I guess because arm64's
original vmemmap_populate() checked only for vmemmap_verify() as well. So probably
this does not need a "Fixes: " tag.