sparc, sparc64: use arch/sparc/include

The majority of this patch was created by the following script:

***
ASM=arch/sparc/include/asm
mkdir -p $ASM
git mv include/asm-sparc64/ftrace.h $ASM
git rm include/asm-sparc64/*
git mv include/asm-sparc/* $ASM
sed -ie 's/asm-sparc64/asm/g' $ASM/*
sed -ie 's/asm-sparc/asm/g' $ASM/*
***

The rest was an update of the top-level Makefile to use sparc
for header files when sparc64 is being build.
And a small fixlet to pick up the correct unistd.h from
sparc64 code.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

arch/sparc/include/asm/current.h

@@ -0,0 +1,34 @@
+/* include/asm/current.h
+ *
+ * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ * Copyright (C) 2002 Pete Zaitcev (zaitcev@yahoo.com)
+ * Copyright (C) 2007 David S. Miller (davem@davemloft.net)
+ *
+ *  Derived from "include/asm-s390/current.h" by
+ *  Martin Schwidefsky (schwidefsky@de.ibm.com)
+ *  Derived from "include/asm-i386/current.h"
+*/
+#ifndef _SPARC_CURRENT_H
+#define _SPARC_CURRENT_H
+
+#include <linux/thread_info.h>
+
+#ifdef CONFIG_SPARC64
+register struct task_struct *current asm("g4");
+#endif
+
+#ifdef CONFIG_SPARC32
+/* We might want to consider using %g4 like sparc64 to shave a few cycles.
+ *
+ * Two stage process (inline + #define) for type-checking.
+ * We also obfuscate get_current() to check if anyone used that by mistake.
+ */
+struct task_struct;
+static inline struct task_struct *__get_current(void)
+{
+	return current_thread_info()->task;
+}
+#define current __get_current()
+#endif
+
+#endif /* !(_SPARC_CURRENT_H) */