Silence cppcheck 2.2 false positive in udp_recv()

Silence cppcheck 2.2 false positive in udp_recv()

cppcheck 2.2 reports the following false positive:

    lib/dns/dispatch.c:1220:14: warning: Either the condition 'resp==NULL' is redundant or there is possible null pointer dereference: resp. [nullPointerRedundantCheck]
     if (disp != resp->disp) {
                 ^
    lib/dns/dispatch.c:1191:11: note: Assuming that condition 'resp==NULL' is not redundant
     if (resp == NULL) {
              ^
    lib/dns/dispatch.c:1220:14: note: Null pointer dereference
     if (disp != resp->disp) {
                 ^

Apparently this version of cppcheck gets confused about conditional
"goto" statements because line 1220 can never be reached if 'resp' is
NULL.

Move a code block to prevent the above false positive from being
reported without affecting the processing logic.

(cherry picked from commit 0b6216d1c702ef0aaa66a2a1bea70cfb12c81468)