reader: Canonicalizing a type once is enough

reader: Canonicalizing a type once is enough

While looking at something else, I noticed that the abixml reader was
trying to canonicalize each type twice.  Once should be enough.

	* src/abg-reader.cc (build_type): Don't try to canonicalize the
	type here because all the sub-routines of this function (which
	actually build the type) already try to canonicalize it.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>