staging/rdma/hfi1: Wrong cast breaks desired pointer arithmetic

The address being mapped into a process's memory for notification events was
improperly calculated due to cast that was happening too early. dd->events is a
pointer and should have been casted to unsigned long after the pointer
arithmetic was done, not before.

As a result, processes were looking at the wrong place and not seeing their
notification events.
Signed-off-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rdma/hfi1/file_ops.c

@@ -607,9 +607,9 @@ static int hfi1_file_mmap(struct file *fp, struct vm_area_struct *vma)
 		 * Use the page where this context's flags are. User level
 		 * knows where it's own bitmap is within the page.
 		 */
-		memaddr = ((unsigned long)dd->events +
-			   ((uctxt->ctxt - dd->first_user_ctxt) *
-			    HFI1_MAX_SHARED_CTXTS)) & PAGE_MASK;
+		memaddr = (unsigned long)(dd->events +
+					  ((uctxt->ctxt - dd->first_user_ctxt) *
+					   HFI1_MAX_SHARED_CTXTS)) & PAGE_MASK;
 		memlen = PAGE_SIZE;
 		/*
 		 * v3.7 removes VM_RESERVED but the effect is kept by