ARM: at91: collect SoC sources into mach-at91

This commit moves source files as follows:

  arch/arm/cpu/arm920t/at91/*   -> arch/arm/mach-at91/arm920t/*
  arch/arm/cpu/arm926ejs/at91/* -> arch/arm/mach-at91/arm926ejs/*
  arch/arm/cpu/armv7/at91/*     -> arch/arm/mach-at91/armv7/*
  arch/arm/cpu/at91-common/*    -> arch/arm/mach-at91/*

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Andreas Bießmann <andreas.devel@googlemail.co>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 5da2c23..f4e9af6 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -4,6 +4,7 @@
 
 # Machine directory name.  This list is sorted alphanumerically
 # by CONFIG_* macro name.
+machine-$(CONFIG_ARCH_AT91)		+= at91
 
 machdirs := $(patsubst %,arch/arm/mach-%/,$(machine-y))