powerpc: Add missing prototype for arch_dup_task_struct()
In commit
55ccf3fe3f9a ("fork: move the real prepare_to_copy() users to
arch_dup_task_struct()") a new arch_dup_task_struct() was added
without a prototype declared in thread_info.h header. Fix the
following warning (treated as error in W=1):
arch/powerpc/kernel/process.c:1609:5: error: no previous prototype for ‘arch_dup_task_struct’
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>