[ARM] No need to include asm/proc-fns.h into asm/system.h

In the old days when arm26/arm32 was combined into the same
architecture, proc-fns.h provided the xchg implementation for
arm26 CPUs.  Since we no longer combine these two, this include
is no longer required.  Remove it.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/asm-arm/system.h

@@ -93,15 +93,15 @@ void hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int,
 				       struct pt_regs *),
 		     int sig, const char *name);
 
-#include <asm/proc-fns.h>
-
 #define xchg(ptr,x) \
 	((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
 
 #define tas(ptr) (xchg((ptr),1))
 
 extern asmlinkage void __backtrace(void);
 extern asmlinkage void c_backtrace(unsigned long fp, int pmode);
+
+struct mm_struct;
 extern void show_pte(struct mm_struct *mm, unsigned long addr);
 extern void __show_regs(struct pt_regs *);