arm64: dts: renesas: salvator-xs: enable SATA

Add the nodes to enable SATA. Note that MD12 (SW12-7) must be switched
off for that to work.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>