IB/hfi1: Move structure and MACRO definitions in user_sdma.c to user_sdma.h

Clean up user_sdma.c by moving the structure and MACRO definitions into
the header file user_sdma.h

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>