subsys/console: Yield on char availability.

If this is not done, there is common pattern that on big input block
(e.g. from a clipboard paste), IRQ routine is called in a tight loop,
leading to circular buffer overflow.

Change-Id: I69a7aa78081b8d74652406f3b3a577ddaf4c5f6f
Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

subsys/console/getchar.c

@@ -30,6 +30,10 @@ static int console_irq_input_hook(uint8_t c)
 	uart_ringbuf[i_put] = c;
 	i_put = i_next;
 	k_sem_give(&uart_sem);
+	/** Allow waiting threads to pick up a char ASAP, or there can be
+	 *  buffer overflow.
+	 */
+	k_yield();
 
 	return 1;
 }