gpio: ts4900: Add hardware dependencies

All the boards supported by the gpio-ts4900 driver are i.MX6 boards,
so only offer the driver for building on this platform, unless
build-testing.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Lucile Quirion <lucile.quirion@savoirfairelinux.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -802,6 +802,7 @@ config GPIO_TPIC2810
 
 config GPIO_TS4900
 	tristate "Technologic Systems FPGA I2C GPIO"
+	depends on SOC_IMX6 || COMPILE_TEST
 	select REGMAP_I2C
 	help
 	  Say yes here to enabled the GPIO driver for Technologic's FPGA core.