remoteproc: fix vdev reference management

remoteproc: fix vdev reference management

Commit 2b45cef5868a ("remoteproc: Further extend the vdev life cycle")
extends kref support for vdev management.
It introduces a regression when following sequence is executed:
rproc_boot --> rproc_shutdown --> rproc_boot
Second rproc_boot call crashes on register_virtio_device as device
is already existing.
Issue is previous vdev is never released when rproc is stop because
associated refcount is too high.

kref_get introduces is not needed as kref_init already initializes
krefcount to 1 because it considers associated variable as used.
This introduces a misalignment between kref_get and kref_put calls.

Fixes: 2b45cef5868a ("remoteproc: Further extend the vdev life cycle")
Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>