x86: ptrace.c: fix defined-but-unused warnings

arch/x86/kernel/ptrace.c:548: warning: 'ptrace_bts_get_size' defined but not used
arch/x86/kernel/ptrace.c:558: warning: 'ptrace_bts_read_record' defined but not used
arch/x86/kernel/ptrace.c:607: warning: 'ptrace_bts_clear' defined but not used
arch/x86/kernel/ptrace.c:617: warning: 'ptrace_bts_drain' defined but not used
arch/x86/kernel/ptrace.c:720: warning: 'ptrace_bts_config' defined but not used
arch/x86/kernel/ptrace.c:788: warning: 'ptrace_bts_status' defined but not used

Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>