There were multiple copy of the same code spread over the different
architectures handling the vDSO.

This patch is merging the duplicated code in arch/*/vdso-pie.c and
arch/*/include/asm/vdso.h in the common files and let only the architecture
specific part in the arch/*/* files.

The file are now organized this way:

include/asm-generic/vdso.h
	contains basic definition which could be overwritten by
	architectures.

arch/*/include/asm/vdso.h
	contains per architecture definitions.
	It may includes include/asm-generic/vdso.h

pie/util-vdso.c
include/util-vdso.h
	These files contains code and definitions common to both criu and
	the parasite code.
	The file include/util-vdso.h includes arch/*/include/asm/vdso.h.

pie/parsite-vdso.c
include/parasite-vdso.h
	contains code and definition specific to the parasite code handling
	the vDSO.
	The file include/parasite-vdso.h includes include/util-vdso.h.

arch/*/vdso-pie.c
	contains the architecture specific code installing the vDSO
	trampoline.

vdso.c
include/vdso.h
	contains code and definition specific to the criu code handling the
	vDSO.
	The file include/vdso.h includes include/util-vdso.h.

CC: Christopher Covington <cov@codeaurora.org>
CC: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>