uprobe: gate bpf call behind BPF_EVENTS

The call into bpf from uprobes needs to be gated now that it doesn't use
the trace_events.h helpers.

Randy found this as a randconfig build failure on linux-next [1].

[1]: https://lore.kernel.org/linux-next/[e-mail]/

Reported-by: Randy Dunlap <[e-mail]>
Signed-off-by: Delyan Kratunov <[e-mail]>
Tested-by: Randy Dunlap <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

kernel/trace/trace_uprobe.c

···
 	int size, esize;
 	int rctx;
 
+#ifdef CONFIG_BPF_EVENTS
 	if (bpf_prog_array_valid(call)) {
 		u32 ret;
 
···
 		if (!ret)
 			return;
 	}
+#endif /* CONFIG_BPF_EVENTS */
 
 	esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));