ftrace: Add MAINTAINERS entries for all ftrace headers

ftrace: Add MAINTAINERS entries for all ftrace headers

There is currently no entry for ftrace_irq.h and ftrace_regs.h. Add a
generic entry for all *ftrace* headers to include them and prevent
overlooking future ftrace headers.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://patch.msgid.link/20260305093117.853700-1-jmarchan@redhat.com
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>