Revert "cmd/internal/ld: put read-only relocated data into .data.rel.ro when making a shared object"

This reverts commit 2c2cbb69.

Broke darwin/arm64

Change-Id: Ibd2dea475d6ce6a8b4b40e2da19a83fc0514025d
Reviewed-on: https://go-review.googlesource.com/14301Reviewed-by: Ian Lance Taylor <iant@golang.org>