irda: use msecs_to_jiffies for conversion to jiffies

API compliance scanning with coccinelle flagged:
./net/irda/timer.c:63:35-37: use of msecs_to_jiffies probably perferable

Converting milliseconds to jiffies by "val * HZ / 1000" 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. Further the () around the arithmetic expression
was dropped.

Patch was compile tested for x86_64_defconfig + CONFIG_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>

net/irda/timer.c

@@ -60,8 +60,8 @@ void irlap_start_query_timer(struct irlap_cb *self, int S, int s)
 	 * to avoid messing with for incoming connections requests and
 	 * to accommodate devices that perform discovery slower than us.
 	 * Jean II */
-	timeout = ((sysctl_slot_timeout * HZ / 1000) * (S - s)
-		   + XIDEXTRA_TIMEOUT + SMALLBUSY_TIMEOUT);
+	timeout = msecs_to_jiffies(sysctl_slot_timeout) * (S - s)
+		   + XIDEXTRA_TIMEOUT + SMALLBUSY_TIMEOUT;
 
 	/* Set or re-set the timer. We reset the timer for each received
 	 * discovery query, which allow us to automatically adjust to