i8042: Handle a duplicate power-on-reset response

Sometimes we seem to get 0xaa twice which causes the config read to fail.
This causes chromebook_link to fail to set up the keyboard.

Add a check for this and read the config again when detected.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>