build: rework "headers*.chk" prerequisite in include/

build: rework "headers*.chk" prerequisite in include/

Listing public headers when out-of-tree build are involved becomes
more annoying where every path to every headers needs to start with
"$(srctree)/$(src)", or $(wildcard ) will not work. This means more
repetition. ( "$(srcdir)" is a shortcut for "$(srctree)/$(src)" )

This patch attempt to reduce the amount of duplication and make better
use of make's meta programming capability. The filters are now listed
in a variable and don't have to repeat the path to the headers files
as this is added later as needed.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>