RDMA/core: Make a new module for the uverbs components needed by drivers

RDMA/core: Make a new module for the uverbs components needed by drivers

To maintain the split where ib_uverbs.ko should not be depended on by
drivers, add a new module ib_uverbs_support.ko which contains the driver
called functions that are too large or too rare to be placed in
ib_uverbs_core.ko

Start by moving most of rdma_core.c into this module, making some
adjustments to split it from the actual uverbs FD code.

This was not done originally because we lacked EXPORT_SYMBOL_NS and I had
a fear that drivers would abuse this interface surface.

Link: https://patch.msgid.link/r/4-v3-43aba1969751+1988-ib_uverbs_support_ko_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>