ppc64: fixing build issue

The commit 69d008d5 ("Use run-time page_size() for mremap")
introduces the use of dynamic page size in rst-malloc.c.

The commit also add the include of unistd.h in
arch/aarch64/include/asm/page.h to allow the build to succeed on this
architecture.  Since ppc64 is also using the same way to deal with page
size, the same include is required in arch/ppc64/include/asm/page.h
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
CC: Christopher Covington <cov@codeaurora.org>
Reviewed-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/ppc64/include/asm/page.h

 #ifndef __CR_ASM_PAGE_H__
 #define __CR_ASM_PAGE_H__
 
+#include <unistd.h>
+
 /*
  * Default config for Pseries is to use 64K pages.
  * See kernel file arch/powerpc/configs/pseries_*defconfig