package/lvm2: remove endif that prevents Buildroot to use Makefiles at all

Commit [1] breaks Buildroot Makefile since a Makefile endif has been left
with no sense giving following error:
package/lvm2/lvm2.mk:61: *** extraneous 'endif'.  Stop.

So let's remove that forgotten endif.

[1]: https://git.buildroot.net/buildroot/commit/?id=8a313b019c7d7e898186a8b08f9c25ae0194fa16



Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>