[x32] Emit callq for CALLpcrel32

Summary:
In AT&T annotation for both x86_64 and x32 calls should be printed as
callq in assembly. It's only a matter of correct mnemonic, object output
is ok.

Test Plan: trivial test added

Reviewers: nadav, dschuff, craig.topper

Subscribers: llvm-commits, zinovy.nis

Differential Revision: http://reviews.llvm.org/D5213