auxdisplay: charlcd: delete mdelay in long_sleep

The function long_sleep() calls mdelay() when in an interrupt handler.
But only charlcd_clear_display() and charlcd_init_display calls
long_sleep(), and my tool finds that the two functions
are never called in an interrupt handler.
Thus mdelay() and in_interrupt() are not necessary.

This is found by a static analysis tool named DCNS written by myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

drivers/auxdisplay/charlcd.c

@@ -99,10 +99,7 @@ static atomic_t charlcd_available = ATOMIC_INIT(1);
 /* sleeps that many milliseconds with a reschedule */
 static void long_sleep(int ms)
 {
-	if (in_interrupt())
-		mdelay(ms);
-	else
-		schedule_timeout_interruptible(msecs_to_jiffies(ms));
+	schedule_timeout_interruptible(msecs_to_jiffies(ms));
 }
 
 /* turn the backlight on or off */