Fix include directory path in libdca.pc.in.

Index: libdca/libdca.pc.in
--- libdca/libdca.pc.in.orig
+++ libdca/libdca.pc.in
@@ -8,4 +8,4 @@ Description: A decoding library for DTS Coherent Acous
 Version: @VERSION@
 Libs: -L${libdir} -ldca
 Libs.private: @LIBDCA_LIBS@
-Cflags: -I${includedir}/@PACKAGE@
+Cflags: -I${includedir}
