remoteproc: stm32: Constify st_rproc_ops

The only usage of st_rproc_ops is to pass its address to rproc_alloc()
which accepts a const pointer. Make it const to allow the compiler to
put it in read-only memory.

Acked-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20201107233630.9728-3-rikard.falkeborn@gmail.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>