ar71xx: image: use a common macro for Cameo AP94 based devices

The Image/Build/DIR825B1 and the Image/Build/DLRTDEV macros
are identical. Merge those into a new Image/Build/CameoAP94
macro, and update the device profiles to use the new macro.
Also rename the dir825b1_* mtdlayout macros to cameo_ap94_*.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38150 3c298f89-4303-0410-b956-a3cf2f4a3e73
ar71xx: image: update Image/Build/CameoAP94 macro

 - append the root squashfs directly after the kernel,
 - use the 64kraw template instead of the 64k,
 - ensure that the generated images have enough erase blocks
   for JFFS2 garbage collection,

Tested on a TEW-673GRU board.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38151 3c298f89-4303-0410-b956-a3cf2f4a3e73