clk: Drop duplicate selection in Kconfig

There is no need to select RATIONAL in individual drivers,
since common clock symbol does it already.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200614115140.41262-1-andriy.shevchenko@linux.intel.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/Kconfig

@@ -120,7 +120,6 @@ config COMMON_CLK_SI5351
 	tristate "Clock driver for SiLabs 5351A/B/C"
 	depends on I2C
 	select REGMAP_I2C
-	select RATIONAL
 	help
 	  This driver supports Silicon Labs 5351A/B/C programmable clock
 	  generators.
@@ -162,7 +161,6 @@ config COMMON_CLK_CDCE706
 	tristate "Clock driver for TI CDCE706 clock synthesizer"
 	depends on I2C
 	select REGMAP_I2C
-	select RATIONAL
 	help
 	  This driver supports TI CDCE706 programmable 3-PLL clock synthesizer.