x86: apl: Use const for driver operations

Update these declarations to const to ensure that the data ends up in the
rodata section.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/intel_common/p2sb.c b/arch/x86/cpu/intel_common/p2sb.c
index e6edab0..3765eee 100644
--- a/arch/x86/cpu/intel_common/p2sb.c
+++ b/arch/x86/cpu/intel_common/p2sb.c
@@ -180,7 +180,7 @@
 	return 0;
 }
 
-struct p2sb_ops p2sb_ops = {
+static const struct p2sb_ops p2sb_ops = {
 	.set_hide	= intel_p2sb_set_hide,
 };