MIPS: Fix for an ARM register allocation bug.

MIPS: Fix for an ARM register allocation bug.

Port r10374 (03bbe39).

Note: the MIPS version was not affected by the bug. This is merely a style cleanup.

Original commit message:
An off-by-one in the register allocator could lead to allocating (and
clobbering) the reserved 0.0 double register.  This required a function with
14 or more live double values.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9150025
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10440 ce2b1a6d-e550-0410-aec6-3dcde31c8c00