pinctrl: actions: Fix Kconfig dependency and help text

1. Fix Kconfig dependency for Actions Semi S900 pinctrl driver which
generates below warning in x86:

WARNING: unmet direct dependencies detected for PINCTRL_OWL
  Depends on [n]: PINCTRL [=y] && (ARCH_ACTIONS || COMPILE_TEST [=n]) && OF [=n]
  Selected by [y]:
  - PINCTRL_S900 [=y] && PINCTRL [=y]

2. Add help text for OWL pinctrl driver
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/actions/Kconfig

 config PINCTRL_OWL
-	bool
+	bool "Actions Semi OWL pinctrl driver"
 	depends on (ARCH_ACTIONS || COMPILE_TEST) && OF
 	select PINMUX
 	select PINCONF
 	select GENERIC_PINCONF
+	help
+	  Say Y here to enable Actions Semi OWL pinctrl driver
 
 config PINCTRL_S900
 	bool "Actions Semi S900 pinctrl driver"
-	select PINCTRL_OWL
+	depends on PINCTRL_OWL
 	help
 	  Say Y here to enable Actions Semi S900 pinctrl driver