clk: gpio-gate: Ensure gpiod_ APIs are prototyped

The gpio-gate clock uses the gpiod_ APIs but does not directly include the
header for them causing build failures in some configurations including ARM
allnoconfig. Include the header directly.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>