net: coap: Remove resource pointer NULL check

This commit removes the resource pointer NULL check inside the resource
enumeration loop of the `coap_well_known_core_get` function because the
expression `(resource + 1)` will never evaluate to NULL (aka. 0).

This fixes the "comparison will always evaluate as ‘true’ for the
pointer operand" warning generated by the GCC 12.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: stephanosio

subsys/net/lib/coap/coap_link_format.c

@@ -687,7 +687,7 @@ int coap_well_known_core_get(struct coap_resource *resource,
 			return r;
 		}
 
-		if ((resource + 1) && (resource + 1)->path) {
+		if ((resource + 1)->path) {
 			r = append_u8(response, (uint8_t) ',');
 			if (!r) {
 				return -ENOMEM;