[SCSI] aacraid: resolve compiler warnings using ptrdiff_t

Unsigned long is not always the same size as a pointer, namely on 32 bit
systems with 64 bit address space. Ptrdiff_t is the same size as a
pointer in all configurations. By using ptrdiff_t we can mitigate the
warning messages on these configurations. There should be no side
effects of this patch.

Signed-off-by: Mark Salyzyn <aacraid@adaptec.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/aacraid/commctrl.c b/drivers/scsi/aacraid/commctrl.c
index 987e35e..72b0393 100644
--- a/drivers/scsi/aacraid/commctrl.c
+++ b/drivers/scsi/aacraid/commctrl.c
@@ -391,10 +391,8 @@
 		/*
 		 *	Extract the fibctx from the input parameters
 		 */
-		if (fibctx->unique == (u32)(unsigned long)arg) {   
-			/* We found a winner */
+		if (fibctx->unique == (u32)(ptrdiff_t)arg) /* We found a winner */
 			break;
-		}
 		entry = entry->next;
 		fibctx = NULL;
 	}