Since the switch of Address from byte* to uintptr_t, we technically
cannot differentiate between constant field addresses and non-constant
ones.
Thus remove the FIELD_ADDR_CONST macro, and use the identical
FIELD_ADDR instead.

R=jkummerow@chromium.org

Bug: v8:7570
Change-Id: Iea4dde36b42c6d0f0ea80a965806f1dbd7adcd39
Reviewed-on: https://chromium-review.googlesource.com/1032746Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52879}