Revert "lib/rwsem.c: fix compatibility issues with Linux 3.0.y"

This reverts commit 112198236c8b6b5e2580e0ee8b1b1feb8b2c2c22.
Revert "rwsem: steal writing sem for better performance"

This reverts commit 56063823eda69539220347c733db4f2f482035ff.