ipq806x: fix BOARD_NAME spellings

ipq806x: fix BOARD_NAME spellings

the board names used by the upgrade check differ from the device names
in case, so always set them. We can't rely on tolower or similar since
different locales might have different rules for lower case letters, so
set them explicitily.

Fixes sysupgrade rejecting *-sysupgrade.tar because of the difference.

Signed-off-by: Kaspar Schleiser <kaspar@schleiser.de>
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
SVN-Revision: 47381