cmd/compile: 64 bits shifts on arm get wrong results [1.16 backport]

[gopherbot]

@randall77 requested issue #48476 to be considered for backport to the next 1.16 minor release.

@gopherbot please open backport issues

[gopherbot]

Change https://golang.org/cl/351070 mentions this issue: cmd/compile: ensure constant shift amounts are in range for arm

[randall77]

This issue causes miscompilation. It's hard to trigger, but causes the compiler to generate wrong code if it does.

[dmitshur]

Closed by merging 1a6281d to release-branch.go1.16.