gpiolib: turn off legacy interface by default

All users of the legacy interface now select CONFIG_GPIOLIB_LEGACY,
so it can be turned off by default.

Allow turning it on manually for compile testing, in order to keep
the build coverage of the legacy drivers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/gpio/Kconfig

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index e43abb3..2b57ba77 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -12,11 +12,18 @@
 
 	  If unsure, say N.
 
-config GPIOLIB_LEGACY
-	def_bool y
-
 if GPIOLIB
 
+config GPIOLIB_LEGACY
+	bool "Legacy GPIO interfaces" if COMPILE_TEST
+	help
+	  There are a few legacy platforms that use the traditional GPIO
+	  number based interfaces instead of GPIO descriptors.
+	  Say Y here to enable build testing drivers that are specific
+	  to those platforms.
+
+	  If unsure, say N.
+
 config GPIOLIB_FASTPATH_LIMIT
 	int "Maximum number of GPIOs for fast path"
 	range 32 512