uprobes/powerpc: Remove additional trap instruction check

prepare_uprobe() already checks if the underlying unstruction
(on file) is a trap variant. We don't need to check this again.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>