gnome: fix PNG logo installation

sflphone.png wasn't properly installed. This commit fixes that.

Change-Id: I9d6228d3a667527f53a4b19b816c0e93cf1edf93
Refs: #45417

gnome/pixmaps/Makefile.am

@@ -25,6 +25,7 @@ buttons_DATA = current.svg \
 				outgoing_rec.svg \
 				missed.svg \
 				busy.svg \
+				sflphone.png \
 				sflphone.svg \
 				sflphone_small.svg \
 				sflphone_notif.svg \