Use known license string for zlua

The Linux kernel MODULE_LICENSE macro only recognizes a handful of
license strings and "MIT" is not one of the them.  Update the macro
to use "Dual MIT/GPL" which is recognized and what the kernel expects
MIT licensed modules to use.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#11112
Closes openzfs#11113

module/lua/lapi.c

@@ -1300,7 +1300,7 @@ module_exit(lua_fini);
 
 ZFS_MODULE_DESCRIPTION("Lua Interpreter for ZFS");
 ZFS_MODULE_AUTHOR("Lua.org");
-ZFS_MODULE_LICENSE("MIT");
+ZFS_MODULE_LICENSE("Dual MIT/GPL");
 ZFS_MODULE_VERSION(ZFS_META_VERSION "-" ZFS_META_RELEASE);
 
 EXPORT_SYMBOL(lua_absindex);