tools: bootconfig: Add bootconfig command

Add "bootconfig" command which operates the bootconfig
config-data on initrd image.

User can add/delete/verify the boot config on initrd
image using this command.

e.g.
Add a boot config to initrd image
 # bootconfig -a myboot.conf /boot/initrd.img

Remove it.
 # bootconfig -d /boot/initrd.img

Or verify (and show) it.
 # bootconfig /boot/initrd.img

Link: http://lkml.kernel.org/r/157867223582.17873.14342161849213219982.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
[ Removed extra blank line at end of bootconfig.c ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/bootconfig/include/linux/string.h

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SKC_LINUX_STRING_H
+#define _SKC_LINUX_STRING_H
+
+#include <string.h>
+
+/* Copied from lib/string.c */
+static inline char *skip_spaces(const char *str)
+{
+	while (isspace(*str))
+		++str;
+	return (char *)str;
+}
+
+static inline char *strim(char *s)
+{
+	size_t size;
+	char *end;
+
+	size = strlen(s);
+	if (!size)
+		return s;
+
+	end = s + size - 1;
+	while (end >= s && isspace(*end))
+		end--;
+	*(end + 1) = '\0';
+
+	return skip_spaces(s);
+}
+
+#endif