input: i8042: Make sure the keyboard is enabled

Add one more step into the init sequence. This fixes the keyboard on samus,
which otherwise does not work.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/input/i8042.c b/drivers/input/i8042.c
index 661d7fd..03d4840 100644
--- a/drivers/input/i8042.c
+++ b/drivers/input/i8042.c
@@ -134,6 +134,10 @@
 	    kbd_read(I8042_DATA_REG) != KBD_POR)
 		goto err;
 
+	if (kbd_write(I8042_DATA_REG, CMD_DRAIN_OUTPUT) ||
+	    kbd_read(I8042_DATA_REG) != KBD_ACK)
+		goto err;
+
 	/* set AT translation and disable irq */
 	config = kbd_cmd_read(CMD_RD_CONFIG);
 	if (config == -1)