FreeRTOS_DHCP_utest: Fix it for Gcc 11

Symptom:

The call to FreeRTOS_recvfrom_ExpectAndReturn() clearly specifies that
FreeRTOS_recvfrom() shall return the (NULL, 0) slice. But instead,
it returns a random pointer and a lenght of 1.
This happens only with Gcc 11 with AddressSanitizer,
but no other compiler does that with or without AddressSanitizer.

A random hunch:

All other calls to FreeRTOS_recvfrom_ExpectAndReturn() set
cmock_to_return=0 instead of 1.

Last ditch attempt before ditching Gcc 11:

I don't know what cmock_to_return is, but doing the same fixes
the last AddressSanitizer error under Gcc 11 run by CI, and of course
also works for all other builds I'm testing with.

test/unit-test/FreeRTOS_DHCP/FreeRTOS_DHCP_utest.c

@@ -1586,7 +1586,7 @@ void test_vDHCPProcessEndPoint_eWaitingOfferNullUDPBuffer( void )
 
     pxNetworkEndPoints = pxEndPoint;
 
-    FreeRTOS_recvfrom_ExpectAndReturn( xDHCPv4Socket, NULL, 0UL, FREERTOS_ZERO_COPY, NULL, NULL, 1 );
+    FreeRTOS_recvfrom_ExpectAndReturn( xDHCPv4Socket, NULL, 0UL, FREERTOS_ZERO_COPY, NULL, NULL, 0 );
     /* Ignore the buffer argument though. */
     FreeRTOS_recvfrom_IgnoreArg_pvBuffer();