arm64: remove traces of perf_ops_bp

Even though perf_ops_bp was removed/renamed back in commit
b0a873ebbf ("perf: Register PMU implementations"), as part of
v2.6.37, its definition still lives on in some arch headers.

This patch removes the vestigal definition from arm64.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/hw_breakpoint.h

@@ -141,8 +141,6 @@ static inline void ptrace_hw_copy_thread(struct task_struct *task)
 }
 #endif
 
-extern struct pmu perf_ops_bp;
-
 /* Determine number of BRP registers available. */
 static inline int get_num_brps(void)
 {