KVM: PPC: Decrement module refcount if init_vm fails

We increment the reference count for KVM-HV/PR before the call to
kvmppc_core_init_vm. If that function fails we need to decrement the
refcount.

Also remove the check on kvm_ops->owner because try_module_get can
handle a NULL module.

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/20220125155735.1018683-5-farosas@linux.ibm.com