powerpc/ftrace: ensure ftrace record ops are always set for NOPs

When an ftrace call site is converted to a NOP, its corresponding
dyn_ftrace record should have its ftrace_ops pointer set to
ftrace_nop_ops.

Correct the powerpc implementation to ensure the
ftrace_rec_set_nop_ops() helper is called on all successful NOP
initialization paths. This ensures all ftrace records are consistent
before being handled by the ftrace core.

Fixes: eec37961 ("powerpc64/ftrace: Move ftrace sequence out of line")
Suggested-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Naveen N Rao (AMD) <naveen@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250912142740.3581368-2-joe.lawrence@redhat.com