libc: switch back to Krait memmove for A15, Krait, and scorpion

Revert "libc: can't forget scorpion (opt in to denver memmove)"

This reverts commit 80b173e7464bfd04ea454b86f794e19022196349.

Revert "libc: import Denver memmove for Krait and A15"

This reverts commit 689dbbfc2e4e739cf365b924e3692b42f5bbde06.

Change-Id: I41da562926c1480529c1d49990cb4ea8f7cb2516