powerpc/thp: tracing: Hide hugepage events under CONFIG_PPC_BOOK3S_64

powerpc/thp: tracing: Hide hugepage events under CONFIG_PPC_BOOK3S_64

The events hugepage_set_pmd, hugepage_set_pud, hugepage_update_pmd and
hugepage_update_pud are only called when CONFIG_PPC_BOOK3S_64 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.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/20250612101259.0ad43e48@batman.local.home
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>