lib: move list sorting code

lib: move list sorting code

Build the source file always, as by putting it into an archive it still
won't be linked into final binaries when not needed. This way possible
build breakage will be easier to notice, and it's more consistent with
us unconditionally building other library kind of code (e.g. sort() or
bsearch()).

While moving the source file, take the opportunity and drop the
pointless EXPORT_SYMBOL() and an unnecessary #include.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Wei Liu <wl@xen.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>