add include/asm-avr32/xor.h

This patch fixes the following compile error with CONFIG_MD_RAID456
on avr32:

<--  snip  -->

...
  CC [M]  crypto/xor.o
/home/bunk/linux/kernel-2.6/git/linux-2.6/crypto/xor.c:23:21: error: asm/xor.h: No such file or directory
/home/bunk/linux/kernel-2.6/git/linux-2.6/crypto/xor.c: In function 'calibrate_xor_blocks':
/home/bunk/linux/kernel-2.6/git/linux-2.6/crypto/xor.c:131: error: 'XOR_TRY_TEMPLATES' undeclared (first use in this function)
/home/bunk/linux/kernel-2.6/git/linux-2.6/crypto/xor.c:131: error: (Each undeclared identifier is reported only once
/home/bunk/linux/kernel-2.6/git/linux-2.6/crypto/xor.c:131: error: for each function it appears in.)
make[2]: *** [crypto/xor.o] Error 1

<--  snip  -->
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

include/asm-avr32/xor.h

+#ifndef _ASM_XOR_H
+#define _ASM_XOR_H
+
+#include <asm-generic/xor.h>
+
+#endif