ARM: rmobile: Move address of IICDVFS(I2C) to rcar-gen3-base.h

The IICDVFS(I2C) set in r8a7796.h is common in rcar-gen3.
This moves CONFIG_SYS_I2C_SH_BASE0 in rcar-gen3-base.h.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>