h8300: Move gpio.h to gpio-internal.h

The current h8300 GPIO implementation doesn't provide the standard GPIO
API, and in fact provides only direction control rather than normal GPIO
functionality. Currently this is only used by the platform interrupt
implementation rather than by a range of drivers so in preparation for
moving over to gpiolib move the header out of the way of the gpiolib
header, allowing a default GPIO implementation to be provided.

For actual use of these GPIOs with gpiolib a real driver would still need
to be written but there appears to be no current need for this.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>