Use 0-padding for i386 and arm print format specifiers

Summary:
This is used for the other architectures in print_address, but is
missing from i386 and arm.

Reviewers: m.ostapenko, spetrovic

Subscribers: aemerson, rengolin, llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D31977

llvm-svn: 300065