i2c: sh_i2c.c: correct BUSY bit define in ICSR

Correct BUSY bit define in ICSR from (1<<3) to (1<<4).

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