Rename GPIO_SUPPORT to GPIO

Rename these options so that CONFIG_IS_ENABLED can be used with them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
index 14347e7..0b4276c 100644
--- a/arch/arm/mach-exynos/Kconfig
+++ b/arch/arm/mach-exynos/Kconfig
@@ -78,7 +78,7 @@
 
 if ARCH_EXYNOS5
 
-config SPL_GPIO_SUPPORT
+config SPL_GPIO
 	default y
 
 config SPL_LIBCOMMON_SUPPORT