gpio: gpiolib-of: Allow compile testing

Lower dependencies for compile testing.

Signed-off-by: Alexander Stein <alexanders83@web.de>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 37f0378..9776ea5 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -49,7 +49,7 @@
 
 config OF_GPIO
 	def_bool y
-	depends on OF
+	depends on OF || COMPILE_TEST
 
 config GPIO_ACPI
 	def_bool y