gpio: mvebu: fix regmap_update_bits usage

In some place in the driver regmap_update_bits was misused. Indeed the
last argument is not the value of the bit (or group of bits) itself but
the mask value inside the register.

So when setting the bit N, then the value must be BIT(N) and not 1.

CC: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Tested-by: Chris Packham <Chris.Packham@alliedtelesis.co.nz>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>