i2c: sh_mobile: use direct writes when accessing ICE bit

ICE bit is for resetting the module. Other bits don't matter then, so we
don't need to use the iic_set_clr() function but can use iic_wr().

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>