test: Add K210 PLL tests to sandbox defconfigs

This adds the unit test for the K210 PLL to the sandbox defconfigs.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_flattree_defconfig b/configs/sandbox_flattree_defconfig
index 853c944..772230c 100644
--- a/configs/sandbox_flattree_defconfig
+++ b/configs/sandbox_flattree_defconfig
@@ -86,6 +86,8 @@
 CONFIG_AXI_SANDBOX=y
 CONFIG_CLK=y
 CONFIG_CLK_COMPOSITE_CCF=y
+CONFIG_CLK_K210=y
+CONFIG_CLK_K210_SET_RATE=y
 CONFIG_SANDBOX_CLK_CCF=y
 CONFIG_CPU=y
 CONFIG_DM_DEMO=y