[x32] Fix function indirect calls

Summary: Zero-extend register to 64-bit for callq/jmpq.

Test Plan: 3 tests added

Reviewers: nadav, dschuff

Subscribers: llvm-commits, zinovy.nis

Differential Revision: http://reviews.llvm.org/D5355

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217942 91177308-0d34-0410-b5e6-96231b3b80d8