RDMA/efa: Remove redundant udata check from alloc ucontext response

RDMA/efa: Remove redundant udata check from alloc ucontext response

The alloc ucontext flow is always called with a valid udata, there's no
need to test whether it's NULL.

While at it, the 'udata->outlen' check is removed as well as we copy the
minimum between the size of the response and outlen, so in case of zero
outlen, zero bytes will be copied.

Link: https://lore.kernel.org/r/20200818110835.54299-1-galpress@amazon.com
Reviewed-by: Firas JahJah <firasj@amazon.com>
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>