IB/hfi1: Clean up hfi1_user_exp_rcv_setup function

Clean up hfi1_user_exp_rcv_setup function by moving page pinning and
unpinning related code to separate functions. In order to reduce the
number of parameters passed between functions, a new data structure
struct tid_user_buf is defined and used.

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>