npapi: fix vlcpp fetch

VLC itself has no submodules

(cherry picked from commit 1f51cbc7439fbcd19d8a33c7a2809401951c8f76)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

extras/package/npapi.am

@@ -11,7 +11,8 @@ fetch-npapi:
 		git reset --hard origin/master; \
 		git submodule update; \
 	else \
-		git clone git://git.videolan.org/npapi-vlc.git npapi-vlc ; \
+		git clone git://git.videolan.org/npapi-vlc.git npapi-vlc && \
+		cd npapi-vlc && \
 		git submodule update --init; \
 	fi
 	git --git-dir=npapi-vlc/.git describe --long --always > stamp-npapi.tmp