net: ieee802154: 6lowpan: remove redundant pointers 'fq' and 'net'

Pointers fq and net are being assigned but are never used hence they
are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'fq' set but not used [-Wunused-but-set-variable]
warning: variable 'net' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>