hw_breakpoint: Remove unused __register_perf_hw_breakpoint() declaration

Commit:

  b326e95 ("hw-breakpoints: Use overflow handler instead of the event callback")

removed __register_perf_hw_breakpoint() function usage and replaced it
with register_perf_hw_breakpoint() function.

Remove the left-over unused __register_perf_hw_breakpoint() declaration
from <linux/hw_breakpoint.h> as well.

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/1594971060-14180-1-git-send-email-bhsharma@redhat.com

Author: Bhupesh Sharma

include/linux/hw_breakpoint.h

@@ -72,7 +72,6 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
 			    void *context);
 
 extern int register_perf_hw_breakpoint(struct perf_event *bp);
-extern int __register_perf_hw_breakpoint(struct perf_event *bp);
 extern void unregister_hw_breakpoint(struct perf_event *bp);
 extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);
 
@@ -119,8 +118,6 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
 			    void *context)		{ return NULL; }
 static inline int
 register_perf_hw_breakpoint(struct perf_event *bp)	{ return -ENOSYS; }
-static inline int
-__register_perf_hw_breakpoint(struct perf_event *bp) 	{ return -ENOSYS; }
 static inline void unregister_hw_breakpoint(struct perf_event *bp)	{ }
 static inline void
 unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)	{ }