xtensa: ISS: change keyboard polling rate

Polling rate of once per 20 seconds seems to be too low. Increase it to
10 times per second.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NChris Zankel <chris@zankel.net>

arch/xtensa/platforms/iss/console.c

@@ -33,7 +33,7 @@
 #endif
 
 #define SERIAL_MAX_NUM_LINES 1
-#define SERIAL_TIMER_VALUE (20 * HZ)
+#define SERIAL_TIMER_VALUE (HZ / 10)
 
 static struct tty_driver *serial_driver;
 static struct tty_port serial_port;