regulator: rpi-panel-v2: Add missing GPIOLIB dependency

Add missing GPIOLIB dependency reported by the LKP test robot.
This fixes the following report:

"
kismet warnings: (new ones prefixed by >>)
>> kismet: WARNING: unmet direct dependencies detected for GPIO_REGMAP when selected by REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2
   WARNING: unmet direct dependencies detected for GPIO_REGMAP
     Depends on [n]: GPIOLIB [=n]
     Selected by [y]:
     - REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2 [=y] && REGULATOR [=y] && I2C [=y]
"

Fixes: d493058 ("regulator: rpi-panel-v2: Add regulator for 7" Raspberry Pi 720x1280")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506092341.enbNKMOR-lkp@intel.com/
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Link: https://patch.msgid.link/20250609200242.31271-1-marek.vasut+renesas@mailbox.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Marek Vasut

drivers/regulator/Kconfig

@@ -1155,6 +1155,7 @@ config REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY
 
 config REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2
 	tristate "Raspberry Pi 7-inch touchscreen panel V2 regulator"
+	depends on GPIOLIB
 	depends on I2C
 	select GPIO_REGMAP
 	select REGMAP_I2C