Since https://crrev.com/c/1112003, the memory size is stored as size_t
instead of uint32_t in order to support 4GB memories.
This CL fixes Liftoff to load and handle that field as ptrsized field
instead of 32 bit integer.
Drive-by: Fix wrong machine type on Phi in TF wasm compiler.

R=titzer@chromium.org

Bug: v8:8130
Change-Id: I40a92a2c24f6311e05b5e2608a0902674a2ce411
Reviewed-on: https://chromium-review.googlesource.com/1206008
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55702}