RDMA/core: Do not compile ib_core_uverbs without USER_ACCESS

RDMA/core: Do not compile ib_core_uverbs without USER_ACCESS

Remove the entire ib_core_uverbs.c from the build if
CONFIG_INFINIBAND_USER_ACCESS is not set. These functions are only used to
support uverbs and are never callable even if they happen to get linked
in.

Provide inlines for the missing ones to return errors to further push code
elimination in drivers.

Link: https://patch.msgid.link/r/1-v3-43aba1969751+1988-ib_uverbs_support_ko_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>