Standarize on one spelling of symlink error message

It's polite to print the name of the link that wasn't created,
and it makes little sense to print the target.

src/system-update-generator/system-update-generator.c

@@ -36,7 +36,7 @@ static const char *arg_dest = "/tmp";
 
 static int generate_symlink(void) {
         struct stat st;
-        char *p;
+        char _cleanup_free_ *p = NULL;
 
         if (lstat("/system-update", &st) < 0) {
                 if (errno == ENOENT)
@@ -51,13 +51,10 @@ static int generate_symlink(void) {
                 return log_oom();
 
         if (symlink(SYSTEM_DATA_UNIT_PATH "/system-update.target", p) < 0) {
-                free(p);
-                log_error("Failed to create symlink: %m");
+                log_error("Failed to create symlink %s: %m", p);
                 return -errno;
         }
 
-        free(p);
-
         return 0;
 }