amd64: restore previous name of amd64_sysv target

all.h

@@ -40,7 +40,7 @@ enum {
 };
 
 struct Target {
-	char name[8];
+	char name[16];
 	int gpr0;   /* first general purpose reg */
 	int ngpr;
 	int fpr0;   /* first floating point reg */

amd64/targ.c

@@ -13,7 +13,7 @@ amd64_memargs(int op)
 }
 
 Target T_amd64_sysv = {
-	.name = "amd64",
+	.name = "amd64_sysv",
 	.gpr0 = RAX,
 	.ngpr = NGPR,
 	.fpr0 = XMM0,