ARM: dts: imx53: add srtc node

rtc-mxc_v2 driver will add support for the i.MX53 SRTC

Note: we keep the 'srtc' label to avoid duplicate with imx53-m53.dtsi

Signed-off-by: Patrick Bruenn <p.bruenn@beckhoff.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>