gpio: pca954x: fix undefined error code from remove
The recent addition of the regulator support has led to the pca953x_remove
function returning uninitialized data when no platform data pointer is
provided, as gcc warns when using -Wmaybe-uninitialized:
drivers/gpio/gpio-pca953x.c: In function 'pca953x_remove':
drivers/gpio/gpio-pca953x.c:860:9: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]
This restores the previous behavior, returning 0 on success.