arm: rmobile: Add support Alt board

The alt board has R8A7794, 1GB DDR3-SDRAM, USB, Ethernet, QSPI,
MMC, SDHI and more.

This commit supports the following functions:
 - DDR3-SDRAM
 - SCIF
 - I2C
 - Ethernet
 - QSPI

Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
6 files changed