'struct scmi_voltage_proto_ops' is not modified in this driver.

Constifying this structure moves some data to a read-only section, so
increases overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig, as an example:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  13142	   1808	      0	  14950	   3a66	drivers/firmware/arm_scmi/voltage.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  13238	   1712	      0	  14950	   3a66	drivers/firmware/arm_scmi/voltage.o

Signed-off-by: Christophe JAILLET <redacted>
---
Compile tested only
---
 drivers/firmware/arm_scmi/voltage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
index fda6a1573609..17127880e10a 100644
--- a/drivers/firmware/arm_scmi/voltage.c
+++ b/drivers/firmware/arm_scmi/voltage.c

@@ -393,7 +393,7 @@ static int scmi_voltage_domains_num_get(const struct scmi_protocol_handle *ph)
 	return vinfo->num_domains;
 }
 
-static struct scmi_voltage_proto_ops voltage_proto_ops = {
+static const struct scmi_voltage_proto_ops voltage_proto_ops = {
 	.num_domains_get = scmi_voltage_domains_num_get,
 	.info_get = scmi_voltage_info_get,
 	.config_set = scmi_voltage_config_set,

-- 
2.50.1