arm64: dts: meson-axg: s400: add missing emmc pwrseq

eMMC pwrseq is defined in the s400 dts but not used in the emmc node.
This is probably just a copy/paste error

Fixes: 221cf34b

 ("ARM64: dts: meson-axg: enable the eMMC controller")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>