common: split _get_hugepagesize into detection and actual query

common: split _get_hugepagesize into detection and actual query

This helper has two parts -- querying the value, and _notrun'ing the
test if huge pages aren't turned on.  Break these into the usual
_require_hugepages and _get_hugepagesize predicates so that we can adapt
xfs/559 to large folios being used for writes.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>