Use relative path rather than hard coded path in package config file

Change-Id: Ia35fadeead69f84f4f4d32ab0c04f2f391aba4f4

libhsakmt.pc.in

@@ -1,4 +1,4 @@
-prefix=@CPACK_PACKAGING_INSTALL_PREFIX@
+prefix=${pcfiledir}/../..
 exec_prefix=${prefix}
 libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
 includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@