IB/rds: Correct ib_api use with gs_dma_address/sg_dma_len

0b088e00 ("RDS: Use page_remainder_alloc() for recv bufs")
added uses of sg_dma_len() and sg_dma_address(). This makes
RDS DOA with the qib driver.

IB ulps should use ib_sg_dma_len() and ib_sg_dma_address
respectively since some HCAs overload ib_sg_dma* operations.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>