feat(drivers/rcar3): ddr: add function to judge a DDR rank

This commit adds the function to change the settings used for DDR
initialization depending on the board ID and DDR rank.

Signed-off-by: Toshiyuki Ogasahara <toshiyuki.ogasahara.bo@hitachi.com>
Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>
Change-Id: I94d550cea620748f5b15499fed1b791a69d61592