Remove jffs-dump.c

Remove jffs-dump.c

This _entire_ file is dead code. The download packages on the FTP
server contain it all the way back to mtd-utils 1.0, but it isn't
built in any of them. The git history (which dates back to 2006)
contains no instance where that file was ever used in a build process.
A quick look at various distribution packages didn't reveal any that
contained a jffs-dump utilty. There have been no major changes to this
file since the initial commit. It won't even compile as it doesn't have
a PROGRAM_NAME defined required by common.h at least since 2010.

At this point, it can be safeley assumed that nobody will miss this.
They had at least 10 years to do something about it.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: Richard Weinberger <richard@nod.at>