clk: fractional-divider: switch to rational best approximation

This patch converts the code to use rational best approximation algorithm which
is much more precise.

Suggested-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 42f7120..bd9f312 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -14,6 +14,7 @@
 	select HAVE_CLK_PREPARE
 	select CLKDEV_LOOKUP
 	select SRCU
+	select RATIONAL
 	---help---
 	  The common clock framework is a single definition of struct
 	  clk, useful across many platforms, as well as an