Add #includes needed to permit the removal of asm/system.h

asm/system.h is a cause of circular dependency problems because it contains
commonly used primitive stuff like barrier definitions and uncommonly used
stuff like switch_to() that might require MMU definitions.

asm/system.h has been disintegrated by this point on all arches into the
following common segments:

 (1) asm/barrier.h

     Moved memory barrier definitions here.

 (2) asm/cmpxchg.h

     Moved xchg() and cmpxchg() here.  #included in asm/atomic.h.

 (3) asm/bug.h

     Moved die() and similar here.

 (4) asm/exec.h

     Moved arch_align_stack() here.

 (5) asm/elf.h

     Moved AT_VECTOR_SIZE_ARCH here.

 (6) asm/switch_to.h

     Moved switch_to() here.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/drivers/misc/sgi-gru/gru_instructions.h b/drivers/misc/sgi-gru/gru_instructions.h
index d95587c..04d5170 100644
--- a/drivers/misc/sgi-gru/gru_instructions.h
+++ b/drivers/misc/sgi-gru/gru_instructions.h
@@ -40,6 +40,7 @@
 			*((volatile unsigned long *)(p)) = v; /* force st.rel */	\
 		} while (0)
 #elif defined(CONFIG_X86_64)
+#include <asm/cacheflush.h>
 #define __flush_cache(p)		clflush(p)
 #define gru_ordered_store_ulong(p, v)					\
 		do {							\