One optimization in the machine-operator-reducer did not consider that
that word32 shift left instructions only consider the last 5 bits of
the shift input.

The issue only occurs for WebAssembly because in JavaScript we always
add a "& 0xf" on the shift value to the TurboFan graph.

For additional background: The JavaScript and WebAssembly spec both
say that only the last 5 bits of the shift value are used in the
word32-shift-left operation. This means that an "x << 0x29", in the
code is actually executed as "x << 0x09". Therefore the changes in
this CL are okay because they mask the last 5 bit of the shift value.

BUG=chromium:689450

Change-Id: Id92f298ed6d7f1714b109b3f4fbcecd5ac6d30f7
Reviewed-on: https://chromium-review.googlesource.com/439312Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43245}