[U-Boot] i2c: Fix pca953x endianess issue, commit daa75b34828d45b7c1d63009188d45f4a32d06ba

This commit broke our pca953x usage(on ppc).

I wonder why gpio pins here has an endian, its not a number. If there must be an endian connected with this, should it not be a cpu_to_be16 instead, which will retain compatibility ?