ar71xx: change some TP-link modelnames (WR841, WA701, WA730)

ar71xx: change some TP-link modelnames (WR841, WA701, WA730)

This patch changes the image-name of some TPlink-routers.
Esp. for the TPlink WR841N + WR841ND some users are confused by the fact
that some images have "nd"-names and others "n"-names only.
In addition this also corrects a missed "D" on WA701 and a "-" for
WA730RE.

backport to CC of
r48767 'http://git.openwrt.org/?p=openwrt.git;a=commit;h=dbd0ab83566291e3b4974f4d4289bb7c93b091d6'
r48768 'http://git.openwrt.org/?p=openwrt.git;a=commit;h=656a17c77d530b14355e8fef4a83265ee2c3271d'
r48769 'http://git.openwrt.org/?p=openwrt.git;a=commit;h=783756e3096a417565d58d78e082a29db10738d4'

Signed-off-by: Sven Roederer <devel-sven@geroedel.de>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@49052 3c298f89-4303-0410-b956-a3cf2f4a3e73