MIPS: Refactor 'clear_page' and 'copy_page' functions.

Remove usage of the '__attribute__((alias("...")))' hack that aliased
to integer arrays containing micro-assembled instructions. This hack
breaks when building a microMIPS kernel. It also makes the code much
easier to understand.

[ralf@linux-mips.org: Added back export of the clear_page and copy_page
symbols so certain modules will work again.  Also fixed build with
CONFIG_SIBYTE_DMA_PAGEOPS enabled.]

Signed-off-by: Steven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3866/
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/mips_ksyms.c

@@ -5,7 +5,7 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (C) 1996, 97, 98, 99, 2000, 01, 03, 04, 05 by Ralf Baechle
+ * Copyright (C) 1996, 97, 98, 99, 2000, 01, 03, 04, 05, 12 by Ralf Baechle
  * Copyright (C) 1999, 2000, 01 Silicon Graphics, Inc.
  */
 #include <linux/interrupt.h>
@@ -34,6 +34,12 @@ EXPORT_SYMBOL(memmove);
 
 EXPORT_SYMBOL(kernel_thread);
 
+/*
+ * Functions that operate on entire pages.  Mostly used by memory management.
+ */
+EXPORT_SYMBOL(clear_page);
+EXPORT_SYMBOL(copy_page);
+
 /*
  * Userspace access stuff.
  */