armv6: REX routines are currently broken, use alternatives

Change-Id: I7ac05ab6add7802a4cc24fe36f7181e7cdfe07e0
Revert "Add new optimized strlen for arm."

This reverts commit 9765bacd6b80be7a59ac0d33c89c194a781d1da9.
libc: krait: Use performance version of bcopy and memmove

Change-Id: I587085aeb0c30ceccaa3f420594a194b129632b5
libc: krait: Restore prior version of strcmp.

Change-Id: I8ddcdb4d3a905dd746985435dcdb525ab5a1c947