libupnpp: fix license

Add license hash and fix LICENSE: since November 2016 (release 0.15.2),
libupnpp is licensed under LGPL-2.1+ and not GPL-2.0+

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libupnpp/libupnpp.hash

@@ -1,2 +1,5 @@
 # Hashes from: http://www.lesbonscomptes.com/upmpdcli/downloads/libupnpp-0.16.0.tar.gz.sha256
 sha256  b34b179e69c46993cf360da9e85db646b03c15ab2927b19eb70e27bf3c359017  libupnpp-0.16.0.tar.gz
+
+# Hash for license file:
+sha256  00a89b0d18aacd4114decf79122db87bf35bddaf2bc50e383c9c9f4c263390b2  COPYING

package/libupnpp/libupnpp.mk

@@ -6,7 +6,7 @@
 
 LIBUPNPP_VERSION = 0.16.0
 LIBUPNPP_SITE = http://www.lesbonscomptes.com/upmpdcli/downloads
-LIBUPNPP_LICENSE = GPL-2.0+
+LIBUPNPP_LICENSE = LGPL-2.1+
 LIBUPNPP_LICENSE_FILES = COPYING
 LIBUPNPP_INSTALL_STAGING = YES
 LIBUPNPP_DEPENDENCIES = expat libcurl libupnp