serial: ifx6x60: Free memory when probe fails

When spi_setup() fails it doesn't free ifx_dev and we have a memory
leak. Fix this by freeing ifx_dev before the return.

Signed-off-by: Souptick joarder <jrdr.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>