gpio: pca953x: Clear the polarity invert register at init

gpio: pca953x: Clear the polarity invert register at init

The pca953x_gpio driver uses default value of polarity inversion
register. For some devices like PCA9557 and MAX7310, their polarity
inversion register default value is 0xf0. So for high 4 ports, when
reading their values, the values are inverted as the actual level.

This patch clears the polarity inversion register to 0 at init, so
that the port read and write values are aligned.

Signed-off-by: Ye Li <ye.li@nxp.com>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Acked-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>