arm64: renesas: Enable GPIOLIB to allow GPIO driver selection

The R-Car GPIO driver cannot be enabled when Renesas SoC's ARCH configs
(ARCH_RENESAS, ARCH_R8A7795, ARCH_R8A7796 and ARCH_R8A77965) are enabled
only.

As GPIOs are a critical resource for proper operation on Renesas
platforms, this patch selects GPIOLIB, just like is done for other SoC
vendors, and on Renesas arm32 SoCs.

Reported-by: Alexandru Gheorghe <Alexandru_Gheorghe@mentor.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[geert: Improve patch description]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>