rockchip: Drop unnecessary SPL properties

While we consider whether to drop use of DT in SPL, remove some unwanted
properties. This reduces SPL size by about 250 bytes.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/firefly-rk3288_defconfig b/configs/firefly-rk3288_defconfig
index 0cbc539..4af9120 100644
--- a/configs/firefly-rk3288_defconfig
+++ b/configs/firefly-rk3288_defconfig
@@ -28,7 +28,7 @@
 CONFIG_CMD_FAT=y
 CONFIG_CMD_FS_GENERIC=y
 CONFIG_SPL_OF_CONTROL=y
-CONFIG_OF_SPL_REMOVE_PROPS="pinctrl-0 pinctrl-names clock-names interrupt-parent"
+CONFIG_OF_SPL_REMOVE_PROPS="pinctrl-0 pinctrl-names clock-names interrupt-parent assigned-clocks assigned-clock-rates assigned-clock-parents"
 CONFIG_REGMAP=y
 CONFIG_SPL_REGMAP=y
 CONFIG_SYSCON=y