fix abuses of ptrdiff_t

Use of ptrdiff_t in places like

-                       if (!access_ok(VERIFY_WRITE, u_tmp->rx_buf, u_tmp->len))
+                       if (!access_ok(VERIFY_WRITE, (u8 __user *)
+                                               (ptrdiff_t) u_tmp->rx_buf,
+                                               u_tmp->len))

is wrong; for one thing, it's a bad C (it's what uintptr_t is for; in general
we are not even promised that ptrdiff_t is large enough to hold a pointer,
just enough to hold a difference between two pointers within the same object).
For another, it confuses the fsck out of sparse.

Use unsigned long or uintptr_t instead.  There are several places misusing
ptrdiff_t; fixed.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/scsi/aacraid/dpcsup.c

@@ -254,7 +254,7 @@ unsigned int aac_intr_normal(struct aac_dev * dev, u32 Index)
 			kfree (fib);
 			return 1;
 		}
-		memcpy(hw_fib, (struct hw_fib *)(((ptrdiff_t)(dev->regs.sa)) +
+		memcpy(hw_fib, (struct hw_fib *)(((uintptr_t)(dev->regs.sa)) +
 		  (index & ~0x00000002L)), sizeof(struct hw_fib));
 		INIT_LIST_HEAD(&fib->fiblink);
 		fib->type = FSAFS_NTC_FIB_CONTEXT;