batman-adv: fix TT-TVLV parsing on OGM reception

When accessing a TT-TVLV container in the OGM RX path
the variable pointing to the list of changes to apply is
altered by mistake.

This makes the TT component read data at the wrong position
in the OGM packet buffer.

Fix it by removing the bogus pointer alteration.

Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>