arm: armada-xp: Move SoC headers to mach-mvebu/include/mach

arm: armada-xp: Move SoC headers to mach-mvebu/include/mach

Move arch/arm/include/asm/arch-armada-xp/*
     -> arch/arm/mach-mvebu/include/mach/*

Additionally the SYS_SOC is renamed from "armada-xp" to "mvebu". With this
change all these files can better be shared with other, newer Mavell
MVEBU SoC's. Like the upcoming Armada 38x support.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Kevin Smith <kevin.smith@elecsyscorp.com>
Tested-by: Dirk Eibach <dirk.eibach@gdsys.cc>