IB/hfi1: Remove intermediate var in hfi1_user_sdma_alloc_queues()

* Pass a product for a call of the function "vmalloc_user" without storing
  it in an intermediate variable.

* Delete the local variable "memsize" which became unnecessary with
  this refactoring.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Doug Ledford <dledford@redhat.com>