modules: rename packages/kernel_modules to packages/lkmc

Then inside, split packages/lkmc into kernel_modules and userland,
to keep userland out of the kernel_modules parent path, which makes no
sense.

Copy built modules and userland to the output rootfs overlay.

Document Linux distro tradeoffs.

packages/lkmc/userland/m5ops.c

@@ -0,0 +1,36 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#m5ops-instructions */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "m5ops.h"
+
+int main(int argc, char **argv)
+{
+	char action;
+	if (argc > 1) {
+		action = argv[1][0];
+	} else {
+		action = 'e';
+	}
+	switch (action)
+	{
+		case 'c':
+			m5_checkpoint();
+			break;
+		case 'd':
+			m5_dumpstats();
+			break;
+		case 'e':
+			m5_exit();
+			break;
+		case 'f':
+			m5_fail_1();
+			break;
+		case 'r':
+			m5_resetstats();
+			break;
+	}
+	return EXIT_SUCCESS;
+}