Use correct ifdef for ipv4 checksumming

p4src/actions_nat64_generic.p4

@@ -29,7 +29,6 @@ action nat64_icmp6_generic()
 action nat64_generic(ipv4_addr_t src, ipv4_addr_t dst) {
 	hdr.ipv4.setValid();
 
-
     /* Stuff that might need to be fixed */
     hdr.ipv4.version        = (bit<4>)4;
     hdr.ipv4.ihl            = (bit<4>)5;                             // internet header length: 4*5 = 20
@@ -50,7 +49,7 @@ action nat64_generic(ipv4_addr_t src, ipv4_addr_t dst) {
     /* Stuff that should be fine */
 	hdr.ethernet.ethertype  = TYPE_IPV4;
 
-    #ifdef USE_NICO_DELTA_CHECKSUM
+    #ifdef _SUME_SWITCH_P4_
     delta_ipv4_from_v6_to_v4();
     #else
     meta.chk_ipv4 = 1; /* need to calculate the hdrchecksum */