Byteswap operations are used a lot in WASM on big endian
architecture. This CL removed unused 1-byte swapping,
rewrite tests so they have better coverage and cleans up
some other minor things.

TEST=cctest/test-run-wasm/RunWasmTurbofan_I32DivSOnDifferentRegisters

Change-Id: I60466bbd5fe3f64e8e55684265dc43e92fcabc2c
Reviewed-on: https://chromium-review.googlesource.com/1106379
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@mips.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Sreten Kovacevic <sreten.kovacevic@mips.com>
Cr-Commit-Position: refs/heads/master@{#53908}