powerpc: add a missing label in resume_kernel

A label 0 was missed in the patch a9c4e541

 (powerpc/kprobe: Complete
kprobe and migrate exception frame). This will cause the kernel
branch to an undetermined address if there really has a conflict when
updating the thread flags.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Cc: stable@vger.kernel.org
Acked-By: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>