ARM: Fix generating two ldr instructions in place of ldrd.

ARM: Fix generating two ldr instructions in place of ldrd.

When ldrd is not available two ldr instructions are generated. This fixes these in the case where the register used in the memory operand is the same as the first register in the register pair receiving the values.

All tests now run on ARM with the flag --special-command="@ --noenable-vfp3". Running without VFP3 support in the simulator causes more ldrd instructions to be used, and the default build configuration does not utilize ldrd, but generated tow ldr instructions.
Review URL: http://codereview.chromium.org/2078013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4667 ce2b1a6d-e550-0410-aec6-3dcde31c8c00