[Arm] Various cleanups to the Arm assembler backend.
A couple of cleanups to the Arm backend to enable support of extended
OOL constant pools in a following CL.
- Remove instruction pattern extern const's and replace their use with IsXXX()
functions.
- Do calculation of the target address of a load from constant pool in one
place.
- A couple of other small cleanups.
R=ulan@chromium.org
Review URL: https://codereview.chromium.org/
317653003
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21932
ce2b1a6d-e550-0410-aec6-
3dcde31c8c00