Userland: Always call syscall(SC_prctl, ...) with 4 arguments

The arguments are passed on registers, so if we pass only 3 defined
arguments then the fourth argument for the prctl syscall could have
garbage value within it.

To avoid possible bugs, always pass 3 arguments to a raw syscall prctl
call in addition to the prctl sub-option (the first argument).

Userland/Libraries/LibC/assert.cpp

@@ -30,7 +30,7 @@ void __assertion_failed(char const* msg)
         { "assertion", strlen("assertion") },
         { msg, strlen(msg) },
     };
-    syscall(SC_prctl, PR_SET_COREDUMP_METADATA_VALUE, &params, nullptr);
+    syscall(SC_prctl, PR_SET_COREDUMP_METADATA_VALUE, &params, nullptr, nullptr);
     abort();
 }
 }