samples: qmi: Constify static qmi ops

The only usage of qmi_sample_handlers[] and lookup_ops is to pass their
addresses to qmi_handle_init() which accepts const pointers to both
qmi_ops and qmi_msg_handler. Make them const to allow the compiler to
put them in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20201124212954.17750-1-rikard.falkeborn@gmail.com


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