KVM: PPC: Book3S HV: Fix vcore_blocked tracepoint

We removed most of the vcore logic from the P9 path but there's still
a tracepoint that tried to dereference vc->runner.

Fixes: ecb6a720 ("KVM: PPC: Book3S HV P9: Remove most of the vcore logic")
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220328215831.320409-1-farosas@linux.ibm.com