libelf: remove

all dependencies have been converted to use libelf1 now, both have
conflicting paths for their headers shared objects.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@35261 3c298f89-4303-0410-b956-a3cf2f4a3e73