doc: fix broken link to DAPlink reel board fw

The repository to the DAPlink firmware for the reel board has been moved
to the Github organization PHYTEC-Messtechnik-GmbH. This commit replaces
the link in the Zephyr reel board documentation accordingly.

Signed-off-by: Jonas Remmert <j.remmert@phytec.de>
1 file changed