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/kernel_modules/module_info.c

@@ -0,0 +1,22 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#module_info */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+static int myinit(void)
+{
+	/* Set by default based on the module file name. */
+	pr_info("name = %s\n", THIS_MODULE->name);
+	pr_info("version = %s\n", THIS_MODULE->version);
+	/* ERROR: nope, not part of struct module. */
+	/*pr_info("asdf = %s\n", THIS_MODULE->asdf);*/
+	return 0;
+}
+
+static void myexit(void) {}
+
+module_init(myinit)
+module_exit(myexit)
+MODULE_INFO(asdf, "qwer");
+MODULE_VERSION("1.0");
+MODULE_LICENSE("GPL");