arm: rmobile: Add support R8A7790

Renesas R8A7790 is CPU with Cortex-A7 and A15.
This supports the basic register definition and GPIO and
framework of PFC.

Signed-off-by: Kouei Abe <kouei.abe.cp@renesas.com>
Signed-off-by: Ryo Kataoka <ryo.kataoka.wt@renesas.com>
Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
CC: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
CC: Albert Aribaud <albert.u.boot@aribaud.net>