[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/dpcsup.c b/drivers/scsi/aacraid/dpcsup.c
index 4e53f9d..fbf27f5 100644
--- a/drivers/scsi/aacraid/dpcsup.c
+++ b/drivers/scsi/aacraid/dpcsup.c
@@ -256,7 +256,8 @@
 			return 1;
 		}
 		memset(hw_fib, 0, sizeof(struct hw_fib));
-		memcpy(hw_fib, (struct hw_fib *)(((unsigned long)(dev->regs.sa)) + (index & ~0x00000002L)), sizeof(struct hw_fib));
+		memcpy(hw_fib, (struct hw_fib *)(((ptrdiff_t)(dev->regs.sa)) +
+		  (index & ~0x00000002L)), sizeof(struct hw_fib));
 		memset(fib, 0, sizeof(struct fib));
 		INIT_LIST_HEAD(&fib->fiblink);
 		fib->type = FSAFS_NTC_FIB_CONTEXT;