image: if possible use profile name when building .tar.gz images

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38374 3c298f89-4303-0410-b956-a3cf2f4a3e73
ubifs: enable building modular images

Now it is possible to build ubi/ubifs images for only selected boards inside
single target.

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38375 3c298f89-4303-0410-b956-a3cf2f4a3e73