ART: Implement hard float for X86

Use XMM0-XMM3 as parameter registers for float/double on X86.  X86_64
already uses XMM0-XMM7 for parameters.

Change the 'hidden' argument register from XMM0 to XMM7 to avoid a
conflict.

This change was requested to simplify the Optimizing compiler
implementation.

Change-Id: I89ba8ade99b9a8a5b1ad1ee5f5cbfd33d656bfaa
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>