xdp: tracing: Hide some xdp events under CONFIG_BPF_SYSCALL

xdp: tracing: Hide some xdp events under CONFIG_BPF_SYSCALL

The events xdp_cpumap_kthread, xdp_cpumap_enqueue and xdp_devmap_xmit are
only called when CONFIG_BPF_SYSCALL is defined.  As each event can take up
to 5K regardless if they are used or not, it's best not to define them
when they are not used. Add #ifdef around these events when they are not
used.

Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20250612182023.78397b76@batman.local.home
Signed-off-by: Alexei Starovoitov <ast@kernel.org>