i2c: mux: i2c-arb-gpio-challenge: allow compiling w/o OF support

It simplifies some tests.

Signed-off-by: Peter Rosin <peda@axentia.se>
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 1bba95e..55a1094 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -8,7 +8,7 @@
 config I2C_ARB_GPIO_CHALLENGE
 	tristate "GPIO-based I2C arbitration"
 	depends on GPIOLIB || COMPILE_TEST
-	depends on OF
+	depends on OF || COMPILE_TEST
 	help
 	  If you say yes to this option, support will be included for an
 	  I2C multimaster arbitration scheme using GPIOs and a challenge &