RDMA/core: Consolidate ib_create_srq flows

RDMA/core: Consolidate ib_create_srq flows

The uverbs layer largely duplicate the code in ib_create_srq(), with the
slight difference that it passes in a udata. Move all the code together
into ib_create_srq_user() and provide an inline for kernel users, similar
to other create calls.

Link: https://lore.kernel.org/r/20200506082444.14502-6-leon@kernel.org
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>