pinctrl/abx500: use the BIT() macro where appropriate

The BIT() macro provides a simple and easy to read way of
obtaining bit offsets into things like masks and hardware
registers. In this patch we're simply replacing all
instances of '1 << x' with 'bit(x)'.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>