build: purge DESCRIPTION

build: purge DESCRIPTION

DESCRIPTION field has been deprecated since 2007, yet internal exporting
causes intermittent package build failures due to the deprecation check,
even with packages that don't have that fields set. Replace all
DESCRIPTION exports with alternative variables defined through shexport
and shvar helpers and remove the check.

Fixes: 547b127d ("make kernel module packaging code reusable and use it in madwifi")
Fixes: 7558f028 ("DESCRIPTION:= is obselete, so complain if it is used and use TITLE if no description is set")
Fixes: cc435322 ("build: optimize target metadata dump")
Fixes: d081edf7 ("build: clean up and optimize ipkg control generator code")
Signed-off-by: George Sapkin <george@sapk.in>
Link: https://github.com/openwrt/openwrt/pull/21668
Signed-off-by: Robert Marko <robimarko@gmail.com>