RDMA/uverbs: Add a common way to create CQ with umem

RDMA/uverbs: Add a common way to create CQ with umem

Add ioctl command attributes and a common handling for the option to
create CQs with memory buffers passed from userspace. When required
attributes are supplied, create umem and provide it for driver's use.
The extension enables creation of CQs on top of preallocated CPU
virtual or device memory buffers, by supplying VA or dmabuf fd, in a
common way.
Drivers can support this flow by initializing a new create_cq_umem fp
field in their ops struct, with a function that can handle the new
parameter.

Signed-off-by: Michael Margolin <mrgolin@amazon.com>
Link: https://patch.msgid.link/20250708202308.24783-2-mrgolin@amazon.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>