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-rockchip/rk3288/Kconfig b/arch/arm/mach-rockchip/rk3288/Kconfig
index 0ff50fe..0e6150f 100644
--- a/arch/arm/mach-rockchip/rk3288/Kconfig
+++ b/arch/arm/mach-rockchip/rk3288/Kconfig
@@ -78,6 +78,9 @@
 config SPL_LIBCOMMON_SUPPORT
 	default y
 
+config SPL_LIBGENERIC_SUPPORT
+	default y
+
 source "board/chipspark/popmetal_rk3288/Kconfig"
 
 source "board/firefly/firefly-rk3288/Kconfig"