ACPI: add 'const' to several ACPI file_operations

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/ac.c b/drivers/acpi/ac.c
index 24ccf81..96309b9 100644
--- a/drivers/acpi/ac.c
+++ b/drivers/acpi/ac.c
@@ -72,7 +72,7 @@
 	unsigned long state;
 };
 
-static struct file_operations acpi_ac_fops = {
+static const struct file_operations acpi_ac_fops = {
 	.open = acpi_ac_open_fs,
 	.read = seq_read,
 	.llseek = seq_lseek,