dm: gpio: Allow GPIO uclass to be used in SPL

Now that we support driver model in SPL, allow GPIO drivers to be used there
also.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/gpio/Makefile

@@ -6,13 +6,9 @@
 #
 
 ifndef CONFIG_SPL_BUILD
-obj-$(CONFIG_DM_GPIO)		+= gpio-uclass.o
 obj-$(CONFIG_AXP_GPIO)		+= axp_gpio.o
 endif
-/* TODO(sjg@chromium.org): Only tegra supports driver model in SPL */
-ifdef CONFIG_TEGRA_GPIO
 obj-$(CONFIG_DM_GPIO)		+= gpio-uclass.o
-endif
 
 obj-$(CONFIG_AT91_GPIO)	+= at91_gpio.o
 obj-$(CONFIG_INTEL_ICH6_GPIO)	+= intel_ich6_gpio.o