RDMA/core: Add the core support field to METHOD_GET_CONTEXT

Add the core support field to METHOD_GET_CONTEXT, this field should
represent capabilities that are not device-specific.

Return support for optional access flags for memory regions. User-space
will use this capability to mask the optional access flags for
unsupporting kernels.

Link: https://lore.kernel.org/r/1578506740-22188-10-git-send-email-yishaih@mellanox.com


Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>