ARM: generate integer zero in a uniform manner.

ARM: generate integer zero in a uniform manner.

ARM generated integer zero as either Operand(0, RelocInfo::NONE32), or
Operand(0), or Operand::Zero(). My change makes it use only
Operand::Zero().

This has no functional impact, it's pure cleanup.

R= ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=13318

[ulan, 2013-01-07 09:30:14]

LGTM. Thanks for cleaning this up. I will land it for you.