greybus: arche-platform: Fix the MODULE_LICENSE to match with header

The header calls out the license to be GPL v2, while the module declares
itself as "GPL"

Testing Done: Trivial
Signed-off-by: Sandeep Patil <sspatil@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arche-platform.c

@@ -754,6 +754,6 @@ static void __exit arche_exit(void)
 }
 module_exit(arche_exit);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Vaibhav Hiremath <vaibhav.hiremath@linaro.org>");
 MODULE_DESCRIPTION("Arche Platform Driver");