tty: serial: mxs-auart: fix error handling in mxs_auart_probe

If uart_add_one_port() fails in mxs_auart_probe, the clks has
to be disabled.Two clks are previously enabled in mxs_get_clks().
Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Branislav Radocaj <branislav@radocaj.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>