[AArch64] Changes some SchedAlias to WriteRes for Cortex-A57.

Using SchedAliases is convenient and works well for latency and resource
lookup for instructions.  However, this creates an entry in
AArch64WriteLatencyTable with a WriteResourceID of 0, breaking any
SchedReadAdvance since the lookup will fail.

http://reviews.llvm.org/D8043
Patch by Dave Estes <cestes@codeaurora.org>!

llvm-svn: 234594