IB/hfi1: Fix up sdma_init function comment

sdma_init does not take a number of sdma engine parameters,
rather it initializes all of the sdma engines.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>