irda: irda-usb: use msecs_to_jiffies for conversions

API compliance scanning with coccinelle flagged:

Converting milliseconds to jiffies by "val * HZ / 1000" is technically
is not a clean solution as it does not handle all corner cases correctly.
By changing the conversion to use msecs_to_jiffies(val) conversion is
correct in all cases.

in the current code:
  mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / 1000));
for HZ < 100 (e.g. CONFIG_HZ == 64|32 in alpha) this effectively results
in no delay at all.

Patch was compile tested for x86_64_defconfig (implies CONFIG_USB_IRDA=m)

Patch is against 4.1-rc4 (localversion-next is -next-20150522)
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/irda/irda-usb.c

@@ -848,7 +848,9 @@ static void irda_usb_receive(struct urb *urb)
 		 * Jean II */
 		self->rx_defer_timer.function = irda_usb_rx_defer_expired;
 		self->rx_defer_timer.data = (unsigned long) urb;
-		mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / 1000));
+		mod_timer(&self->rx_defer_timer,
+			  jiffies + msecs_to_jiffies(10));
+
 		return;
 	}