package/multipath-tools: fix license

As stated in README.md, multipath-tools is covered by several licenses
and LGPL-2.0 is "just" the default license:
 - GPL-2.0+ (e.g. libmultipath/alias.c)
 - GPL-3.0+ (e.g. libdmmp/libdmmp.c)
 - LGPL-2.1+ (e.g. libmpathcmd/mpath_cmd.c)

So replace COPYING (which is a symlink to LICENSES/LGPL-2.0) by the
approriate license files in LICENSES directory

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr: further split long lines]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>