configfragments.py: Correct the help for enable-fragment

configfragments.py: Correct the help for enable-fragment

The help entry for --quiet had been added to list-fragments rather than
enable-fragment.

Due to the fact that --quiet is a global option, this actually adds a
dummy --quiet option as it would otherwise hide the global option, but
would never be set since any --quiet argument would already have been
parsed when this option is parsed.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>