[ARM] Cortex-A57 scheduling model for ARM backend (AArch32)

This patch implements the Cortex-A57 scheduling model.
The main code is in ARMScheduleA57.td, ARMScheduleA57WriteRes.td.
Small changes in cpp,.h files to support required scheduling predicates.

Scheduling model implemented according to:
 http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf.

Patch by : Andrew Zhogin (submitted on his behalf, as requested).
Rewiewed by: Renato Golin, Diana Picus, Javed Absar, Kristof Beyls.
Differential Revision: https://reviews.llvm.org/D28152

llvm-svn: 304530