i2c: gpio: fix MODULE_LICENCE

Let MODULE_LICENCE match the SPDX header which is correctly based on the
previous textual description.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-gpio.c

@@ -520,5 +520,5 @@ module_exit(i2c_gpio_exit);
 
 MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
 MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:i2c-gpio");