rockchip: spl: Support full-speed CPU in SPL

Add a feature which speeds up the CPU to full speed in SPL to minimise
boot time. This is only supported for certain boards (at present only
jerry).

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/chromebook_jerry_defconfig b/configs/chromebook_jerry_defconfig
index b2672b8..526306f 100644
--- a/configs/chromebook_jerry_defconfig
+++ b/configs/chromebook_jerry_defconfig
@@ -3,6 +3,7 @@
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_ROCKCHIP_RK3288=y
 CONFIG_TARGET_CHROMEBOOK_JERRY=y
+CONFIG_ROCKCHIP_FAST_SPL=y
 CONFIG_SPL_STACK_R_ADDR=0x80000
 CONFIG_DM_KEYBOARD=y
 CONFIG_DEFAULT_DEVICE_TREE="rk3288-jerry"