lib/vsprintf.c: remove %Z support

Now that %z is standartised in C99 there is no reason to support %Z.
Unlike %L it doesn't even make format strings smaller.

Use BUILD_BUG_ON in a couple ATM drivers.

In case anyone didn't notice lib/vsprintf.o is about half of SLUB which
is in my opinion is quite an achievement.  Hopefully this patch inspires
someone else to trim vsprintf.c more.

Link: http://lkml.kernel.org/r/20170103230126.GA30170@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/ethernet/cadence/macb.c

@@ -1622,7 +1622,7 @@ static void macb_init_rx_buffer_size(struct macb *bp, size_t size)
 		}
 	}
 
-	netdev_dbg(bp->dev, "mtu [%u] rx_buffer_size [%Zu]\n",
+	netdev_dbg(bp->dev, "mtu [%u] rx_buffer_size [%zu]\n",
 		   bp->dev->mtu, bp->rx_buffer_size);
 }