clk: uniphier: fix unmet direct dependencies warning

Since commit f0776a5517 ("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>

arch/arm/Kconfig

@@ -1021,7 +1021,6 @@ config TARGET_COLIBRI_PXA270
 config ARCH_UNIPHIER
 	bool "Socionext UniPhier SoCs"
 	select BOARD_LATE_INIT
-	select CLK_UNIPHIER
 	select DM
 	select DM_GPIO
 	select DM_I2C

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