ARM: dts: ls1021a: Enable the esdhc

Ls1021a esdhc had been enabled in uboot,
but it had not been enabled it in kernel,
So set the esdhc's status to "okay".

Signed-off-by: yinbo.zhu <yinbo.zhu@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>