x86/boot: Clean up things used by decompressors

This rearranges the pieces needed to include the decompressor code
in misc.c. It wasn't obvious why things were there, so a comment was
added and definitions consolidated.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1461185746-8017-4-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/boot/compressed/misc.c

@@ -21,19 +21,19 @@
  * it is not safe to place pointers in static structures.
  */
 
+/* Macros used by the included decompressor code below. */
 #define STATIC		static
 
-#undef memcpy
-
 /*
- * Use a normal definition of memset() from string.c. There are already
+ * Use normal definitions of mem*() from string.c. There are already
  * included header files which expect a definition of memset() and by
  * the time we define memset macro, it is too late.
  */
+#undef memcpy
 #undef memset
 #define memzero(s, n)	memset((s), 0, (n))
 
-
+/* Functions used by the included decompressor code below. */
 static void error(char *m);
 
 /*