Kernel: Implement linux's eventfd

userspace/libraries/LibC/sys/eventfd.cpp

@@ -0,0 +1,8 @@
+#include <sys/eventfd.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+int eventfd(unsigned int initval, int flags)
+{
+	return syscall(SYS_EVENTFD, initval, flags);
+}