arm64: mm: remove unused functions and variable protoypes

The functions __cpu_flush_user_tlb_range and __cpu_flush_kern_tlb_range
were removed in commit fa48e6f7 'arm64: mm: Optimise tlb flush logic
where we have >4K granule'. Global variable cpu_tlb was never used in
arm64.

Remove them.
Signed-off-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/tlbflush.h

@@ -24,11 +24,6 @@
 #include <linux/sched.h>
 #include <asm/cputype.h>
 
-extern void __cpu_flush_user_tlb_range(unsigned long, unsigned long, struct vm_area_struct *);
-extern void __cpu_flush_kern_tlb_range(unsigned long, unsigned long);
-
-extern struct cpu_tlb_fns cpu_tlb;
-
 /*
  *	TLB Management
  *	==============