Convert CONFIG_SPL_LIBGENERIC_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
index bf73378..ce2a16f 100644
--- a/arch/arm/mach-exynos/Kconfig
+++ b/arch/arm/mach-exynos/Kconfig
@@ -67,6 +67,9 @@
 config SPL_LIBCOMMON_SUPPORT
 	default y
 
+config SPL_LIBGENERIC_SUPPORT
+	default y
+
 choice
 	prompt "EXYNOS5 board select"