IB/qib: Add err_decode() call for ring dump

Commit 0b3ddf38 ("Log all SDMA errors unconditionally") missed
part of the patch.

This also corrects a format warning when dma_addr_t is 32 bits
on a 64 bit system.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>