svcrdma: Add Fast Reg MR Data Types

Add data types to track Fast Reg Memory Regions. The core data type is
svc_rdma_fastreg_mr that associates a device MR with a host kva and page
list. A field is added to the WR context to keep track of the FRMR
used to map the local memory for an RPC.

An FRMR list and spin lock are added to the transport instance to keep
track of all FRMR allocated for the transport. Also added are device
capability flags to indicate what the memory registration
capabilities are for the underlying device and whether or not fast
memory registration is supported.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>