ath5k: Use usleep_range where possible

Use usleep_range where possible to reduce busy waits

Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath5k/pci.c b/drivers/net/wireless/ath/ath5k/pci.c
index dfa48eb..849fa06 100644
--- a/drivers/net/wireless/ath/ath5k/pci.c
+++ b/drivers/net/wireless/ath/ath5k/pci.c
@@ -98,7 +98,7 @@
 					0xffff);
 			return true;
 		}
-		udelay(15);
+		usleep_range(15, 20);
 	}
 
 	return false;