RDMA/erdma: Add driver to kernel build environment

Add erdma to the kernel build environment, and sort the source
order in drivers/infiniband/Kconfig.

Link: https://lore.kernel.org/r/20220727014927.76564-12-chengyou@linux.alibaba.com
Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>