Revert "Optimized ARM RWSEM algorithm"

This reverts commit 6a180c1e670421c97fc847e8ee1fa7da6e711b36.
Revert "lemur_defconfig: enable RWSEM_XCHGADD"

This reverts commit 51d13c8df48dd835102e0b1ceeda23f3b60812f6.