For ebp, exclude as needed. For esp, don't mark it as
an int register.

Not sure exactly how to do a targeted test for this Om1
register allocator. The Om1 regalloc seems to start w/ a
fresh whitelist after each instruction, so it may assign
the same register (e.g., eax), as an earlier instruction.
Without pre-colored registers, I'm not sure how to force it
to allocate something other than the first few registers.
I do have a test case that has a ton of pre-colored
registers, (e.g., cmpxchg8b), but that is a different CL:
https://codereview.chromium.org/362463002/

Encountered for:
BUG= https://code.google.com/p/nativeclient/issues/detail?id=3882
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/369573005