spl: Introduce SPL_DM_GPIO Kconfig define

This define indicates if DM_GPIO shall be supported in SPL. This allows
proper operation of DM converted GPIO drivers in SPL, which use
boards.

Signed-off-by: Lukasz Majewski <lukma@denx.de>

common/spl/Kconfig

@@ -485,6 +485,12 @@ config SPL_DMA_SUPPORT
 	  the CPU moving the data. Enable this option to build the drivers
 	  in drivers/dma as part of an SPL build.
 
+config SPL_DM_GPIO
+	bool "Support Driver Model GPIO drivers"
+	depends on SPL_GPIO_SUPPORT && DM_GPIO
+	help
+	  Enable support for Driver Model based GPIO drivers in SPL.
+
 config SPL_DRIVERS_MISC_SUPPORT
 	bool "Support misc drivers"
 	help