tools/bootconfig: scripts/ftrace.sh was missing the shebang line, so added it

This file was missing the shebang line, so added it.

Link: https://lore.kernel.org/all/20250722225351.8811-1-unixbhaskar@gmail.com/



[Masami: changed title. ]

Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>