powerpc: dts: p1020/p2020: Fix esdhc node name

For compatibility with Linux kernel DTS files and also with other U-Boot
powerpc DTS files, rename esdhc@2e000 node to sdhc@2e000 in p1020-post.dtsi
and p2020-post.dtsi include files.

Linux kernel DTS files which include these dtsi files, expect that esdhc
node has name sdhc@2e000 and do not work with other node names.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>