gpio: GPIO_SAMA5D2_PIOBU should depend on ARCH_AT91

The SAMA5D2 PIOBU is only present on some AT91/Microchip SoCs.  Hence
add a dependency on ARCH_AT91, to prevent asking the user about this
driver when configuring a kernel without AT91/Microchip SoC support.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/Kconfig

@@ -544,6 +544,7 @@ config GPIO_SAMA5D2_PIOBU
 	tristate "SAMA5D2 PIOBU GPIO support"
 	depends on MFD_SYSCON
 	depends on OF_GPIO
+	depends on ARCH_AT91 || COMPILE_TEST
 	select GPIO_SYSCON
 	help
 	  Say yes here to use the PIOBU pins as GPIOs.