staging: comedi: serial2002: usleep_range is preferred over udelay

Fix checkpatch issue: "CHECK: usleep_range is preferred over udelay;
see Documentation/timers/timers-howto.txt". Replace the udelay() with
usleep_range() with a reasonable upper limit.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/serial2002.c

@@ -175,7 +175,7 @@ static int serial2002_tty_read(struct file *f, int timeout)
 					result = ch;
 					break;
 				}
-				udelay(100);
+				usleep_range(100, 1000);
 			}
 		}
 		set_fs(oldfs);