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/shared/seccomp-util.c

@@ -874,10 +874,10 @@ int seccomp_add_syscall_filter_item(scmp_filter_ctx *seccomp, const char *name,
                 const SyscallFilterSet *other;
 
                 other = syscall_filter_set_find(name);
-                if (!other) {
-                        log_debug("Filter set %s is not known!", name);
-                        return -EINVAL;
-                }
+                if (!other)
+                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "Filter set %s is not known!",
+                                               name);
 
                 return seccomp_add_syscall_filter_set(seccomp, other, action, exclude, log_missing);