acpi/acpigen: Constify CST functions' pointers

The `acpigen_write_CST_package` and `acpigen_write_CST_package_entry`
functions don't modify the provided C-state information. So, make the
pointer parameters read-only to enforce this. Also constify arguments
where possible.

Change-Id: I9e18d82ee6c16e4435b8fad6d467e58c33194cf4
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58391
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/soc/amd/picasso/acpi.c

@@ -289,7 +289,7 @@ void generate_cpu_entries(const struct device *device)
 		.addrl = PS_STS_REG,
 	};
 
-	acpi_cstate_t cstate_info[] = {
+	const acpi_cstate_t cstate_info[] = {
 		[0] = {
 			.ctype = 1,
 			.latency = 1,