batman-adv: Use octal permissions instead of macros

Linus prefers to have octal permission numbers instead of combinations of
macro names ("random line noise"). Also old existing "bad symbolic
permission bit macro use" should be converted to octal numbers.
(http://lkml.kernel.org/r/CA+55aFw5v23T-zvDZp-MmD_EYxF8WbafwwB59934FV7g21uMGQ@mail.gmail.com

)

Also remove the S_IFREG bit from the octal representation because it is
filtered out by debugfs_create.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>