IB/ehca: Change meaning of hca_cap_mr_pgsize

ehca_shca.hca_cap_mr_pgsize now contains all supported page sizes ORed
together. This makes some checks easier to code and understand, plus
we can return this value verbatim in query_hca(), fixing a problem
with SRP (reported by Anton Blanchard -- thanks!).

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>