coccinelle: make use of SYNTHETIC_ERRNO

Ideally, coccinelle would strip unnecessary braces too. But I do not see any
option in coccinelle for this, so instead, I edited the patch text using
search&replace to remove the braces. Unfortunately this is not fully automatic,
in particular it didn't deal well with if-else-if-else blocks and ifdefs, so
there is an increased likelikehood be some bugs in such spots.

I also removed part of the patch that coccinelle generated for udev, where we
returns -1 for failure. This should be fixed independently.

src/basic/process-util.c

@@ -1227,8 +1227,7 @@ int must_be_root(void) {
         if (geteuid() == 0)
                 return 0;
 
-        log_error("Need to be root.");
-        return -EPERM;
+        return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be root.");
 }
 
 int safe_fork_full(