remoteproc: Clone rproc_ops in rproc_alloc()

In order to allow rproc_alloc() to, in a future patch, update entries in
the "ops" struct we need to make a local copy of it.

Reviewed-By: Loic Pallardy <loic.pallardy@st.com>
Tested-By: Loic Pallardy <loic.pallardy@st.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>