IFUNC for Cavium ThunderX2

IFUNC for Cavium ThunderX2

	* sysdeps/aarch64/multiarch/Makefile (sysdep_routines):
	Add memcpy_thunderx2.
	* sysdeps/aarch64/multiarch/ifunc-impl-list.c (MAX_IFUNC):
	Increment to 4.
	(__libc_ifunc_impl_list): Add __memcpy_thunderx2.
	* sysdeps/aarch64/multiarch/memcpy.c (libc_ifunc): Add IS_THUNDERX2
	and IS_THUNDERX2PA checks.
	* sysdeps/aarch64/multiarch/memcpy_thunderx.S (USE_THUNDERX2):
	Use macro to set name appropriately.
	(memcpy): Use USE_THUNDERX2 macro to modify prefetches.
	* sysdeps/aarch64/multiarch/memcpy_thunderx2.S: New file.
	* sysdeps/unix/sysv/linux/aarch64/cpu-features.h (IS_THUNDERX2PA):
	New macro.
	(IS_THUNDERX2): New macro.