In code generator, DEXTM instruction will be emitted for intervals
position=[0,31] and size=[33,64]. In simulator, mask for DEXTM will be
calculated on correct way for size = 64. Disassembler has now possibility
to disassemble instructions DEXTM and DEXTU.

TEST=cctest/test-run-machops/Regression6122
BUG=

Review-Url: https://codereview.chromium.org/2769403002
Cr-Commit-Position: refs/heads/master@{#44137}