RDMA/erdma: Add the erdma module

Add the main erdma module, which provides interface to infiniband
subsystem.

This commit includes a modification from Christophe, that using the bitmap
API to allocate bitmaps instead of hand-writing. And the commit also fixes
warnings reported by static checkers.

Link: https://lore.kernel.org/r/20220727014927.76564-10-chengyou@linux.alibaba.comSigned-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>