debugfs: fix "ls -p" to avoid printing garbage after the file name

debugfs: fix "ls -p" to avoid printing garbage after the file name

In commit 68a1de3df3 (debugfs: pretty print encrypted filenames in the
ls command), a change was introduced in debugfs/ls.c which instead of
copying dirent->name and 0-terminating it, dirent->name is used
directly in printf.

However, instead of using the precision to limit the number of
characters output, the code uses the field width. As a result,
characters are output until a 0 is read, which results in garbage
after the file name.

Also fix two other instances of this in debugging messages that aren't
used, but fixing them will avoid potential future copypasta bugs.

Reported-by: Christian Gabriel <ch_gabriel@web.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>