serial: Allow compile test of GPIO consumers if !GPIOLIB

The GPIO subsystem provides dummy GPIO consumer functions if GPIOLIB is
not enabled. Hence drivers that depend on GPIOLIB, but use GPIO consumer
functionality only, can still be compiled if GPIOLIB is not enabled.

Relax the dependency on GPIOLIB if COMPILE_TEST is enabled, where
appropriate.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1377,7 +1377,8 @@ config SERIAL_ALTERA_UART_CONSOLE
 
 config SERIAL_IFX6X60
         tristate "SPI protocol driver for Infineon 6x60 modem (EXPERIMENTAL)"
-	depends on GPIOLIB && SPI && HAS_DMA
+	depends on GPIOLIB || COMPILE_TEST
+	depends on SPI && HAS_DMA
 	help
 	  Support for the IFX6x60 modem devices on Intel MID platforms.