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-uniphier/Kconfig b/arch/arm/mach-uniphier/Kconfig
index 6deca5b..573d942 100644
--- a/arch/arm/mach-uniphier/Kconfig
+++ b/arch/arm/mach-uniphier/Kconfig
@@ -3,6 +3,9 @@
 config SPL_LIBCOMMON_SUPPORT
 	default y
 
+config SPL_LIBGENERIC_SUPPORT
+	default y
+
 config SYS_CONFIG_NAME
 	default "uniphier"