net: fill in MODULE_DESCRIPTION()s for 6LoWPAN

W=1 builds now warn if module is built without a MODULE_DESCRIPTION().
Add descriptions to IPv6 over Low power Wireless Personal Area Network.

Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240208164244.3818498-5-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/6lowpan/core.c

@@ -179,4 +179,5 @@ static void __exit lowpan_module_exit(void)
 module_init(lowpan_module_init);
 module_exit(lowpan_module_exit);
 
+MODULE_DESCRIPTION("IPv6 over Low-Power Wireless Personal Area Network core module");
 MODULE_LICENSE("GPL");