tools/bootconfig: Add a script to generate ftrace shell-command from bootconfig

Add a bconf2ftrace.sh under tools/bootconfig/scripts which generates
a shell script to setup boot-time trace from bootconfig file for testing
the bootconfig.

bconf2ftrace.sh will take a bootconfig file (includes boot-time tracing)
and convert it into a shell-script which is almost same as the boot-time
tracer does.
If --apply option is given, it also tries to apply those command to the
running kernel, which requires the root privilege (or sudo).

For example, if you just want to confirm the shell commands, save
the output as below.

 # bconf2ftrace.sh ftrace.bconf > ftrace.sh

Or, you can apply it directly.

 # bconf2ftrace.sh --apply ftrace.bconf

Note that some boot-time tracing parameters under kernel.* are not able
to set via tracefs nor procfs (e.g. tp_printk, traceoff_on_warning.),
so those are ignored.

Link: https://lkml.kernel.org/r/159704851101.175360.15119132351139842345.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>