cmd/compile: use NEGL for DIVL

[mdempsky]

When emitting the code to handle x / -1 on amd64, we should use the size-appropriate negation operation. For example, NEGL for DIVL.

This probably also means using NEGW for DIVW, which might also apply to the 386 backend?

Fixing this should allow reverting https://go-review.googlesource.com/c/go/+/85736. See also #23305.

/cc @TocarIP @cherrymui

[gopherbot]

Change https://golang.org/cl/96815 mentions this issue: cmd/compile/internal/amd64: use appropriate NEG for div