clk: uniphier: fix unmet direct dependencies warning

Since commit f0776a551764 ("spl: dm: Kconfig: SPL_CLK depends on
SPL_DM"), the following warning is displayed:

  $ make uniphier_v8_defconfig
  warning: (ARCH_ZYNQ && ARCH_ZYNQMP && STM32F7 && CLK_UNIPHIER) selects
  SPL_CLK which has unmet direct dependencies (CLK && SPL_DM)

While I am here, I am removing the prompt to make it user-unconfigurable
option so that "select CLK_UNIPHIER" can be omitted.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/drivers/clk/uniphier/Kconfig b/drivers/clk/uniphier/Kconfig
index da3e355..3666d84 100644
--- a/drivers/clk/uniphier/Kconfig
+++ b/drivers/clk/uniphier/Kconfig
@@ -1,9 +1,8 @@
 config CLK_UNIPHIER
-	bool "Clock driver for UniPhier SoCs"
+	def_bool y
 	depends on ARCH_UNIPHIER
 	select CLK
-	select SPL_CLK
-	default y
+	select SPL_CLK if SPL
 	help
 	  Support for clock controllers on UniPhier SoCs.
 	  Say Y if you want to control clocks provided by System Control