i2c: sh_i2c.c: support I2C2, I2C3 and I2C4

sh_i2c.c support I2C0 and I2C1. This patch extends it to I2C4.

Acked-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Tetsuyuki Kobayashi <koba@kmckk.co.jp>