tools/bootconfig: Support per-group/all event enabling option

Add group or all event enabling syntax support to bconf2ftrace.sh.
User can pass a bootconfig file which includes

ftrace[.instance.INSTANCE].event.enable

    and

ftrace[.instance.INSTANCE].event.GROUP.enable

correctly.

Link: https://lkml.kernel.org/r/162856127850.203126.16694505101982548237.stgit@devnote2

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