ath5k: correct interrupt storm warning

Ben Greear points out that the "too many interrupts" message will
never print in the intended case since the interrupt counter
will be -1 after the loop.  Change it to pre-decrement so it will
be 0 on the thousandth iteration.

Cc: Ben Greear <greearb@candelatech.com>
Signed-off-by: NBob Copeland <me@bobcopeland.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/base.c

@@ -2505,7 +2505,7 @@ ath5k_intr(int irq, void *dev_id)
 				ath5k_hw_update_mib_counters(ah, &sc->ll_stats);
 			}
 		}
-	} while (ath5k_hw_is_intr_pending(ah) && counter-- > 0);
+	} while (ath5k_hw_is_intr_pending(ah) && --counter > 0);
 
 	if (unlikely(!counter))
 		ATH5K_WARN(sc, "too many interrupts, giving up for now\n");