ath79: Use -v1 suffix for TP-Link WDR3600/4300

In ath79, identifiers tplink_tl-wdr3600 and tplink_tl-wdr4300 have
been used while most other TP-Link devices include the revision.

Although there actually is only one major revision of these
devices, they bear the revision on their bottom (v1.x). TP-Link
also refers to the devices as V1 on its web page.

This patch thus adds -v1 to both so it is more consistent
with other devices and with what you would expect from reading
the on-device sticker and the support pages.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>