i2c: i801: convert to use common P2SB accessor

Since we have a common P2SB accessor in tree we may use it instead of
open coded variants.

Replace custom code by p2sb_bar() call.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Henning Schild <henning.schild@siemens.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>