move doc for inits and sanity checks to README

kernel_module/user/hello.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sanity-checks */
+
 #include <stdio.h>
 #include <stdlib.h>
 

kernel_module/user/hello_cpp.cpp

@@ -1,5 +1,7 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sanity-checks */
+
 #include <iostream>
 
 int main() {
-    std::cout << "hello world" << std::endl;
+    std::cout << "hello cpp" << std::endl;
 }

kernel_module/user/poweroff.c

@@ -1,6 +1,4 @@
-/* Userspace is for the weak. Die.
- * https://stackoverflow.com/questions/28812514/how-to-shutdown-linux-using-c-or-qt-without-call-to-system
- **/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#poweroff-out */
 
 #define _XOPEN_SOURCE 700
 #include <stdio.h>

kernel_module/user/sleep_forever.c

@@ -1,4 +1,4 @@
-/* Sleeping beauty, your prince is called Ctrl + C. */
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sleep_forever-out */
 
 #include <stdio.h>
 #include <unistd.h>