linux-phytec-fsl

ieee802154: 6lowpan_rtnl: fix correct errno value

This patch correct the return value of lowpan_alloc_frag if an error
occur. Errno numbers should always be negative.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>