The XLNX_ZYNQMP config is used in multiple subdirectories
(timer, intc). Move it to the root hw/Kconfig.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190427141459.19728-2-philmd@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>