clk: Add K210 pll support

This pll code is primarily based on the code from the kendryte standalone
sdk in lib/drivers/sysctl.c. k210_pll_calc_config is roughly analogous to
the algorithm used to set the pll frequency, but it has been completely
rewritten to be fixed-point based.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
CC: Lukasz Majewski <lukma@denx.de>
diff --git a/test/dm/Makefile b/test/dm/Makefile
index 6c18fd0..5094a78 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -73,4 +73,5 @@
 obj-$(CONFIG_DM_MDIO) += mdio.o
 obj-$(CONFIG_DM_MDIO_MUX) += mdio_mux.o
 obj-$(CONFIG_DM_RNG) += rng.o
+obj-$(CONFIG_CLK_K210_SET_RATE) += k210_pll.o
 endif