PCI: Constify label attribute_group structures

attribute_groups are not supposed to change at runtime. All functions
working with attribute_groups provided by <linux/sysfs.h> work with const
attribute_group. So mark the non-const structs as const.

File size before:
text data bss dec hex filename
930 320 0 1250 4e2 drivers/pci/pci-label.o

File size After adding 'const':
text data bss dec hex filename
1058 192 0 1250 4ca drivers/pci/pci-label.o

Signed-off-by: Arvind Yadav <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>

drivers/pci/pci-label.c

···
 	NULL,
 };
 
-static struct attribute_group smbios_attr_group = {
+static const struct attribute_group smbios_attr_group = {
 	.attrs = smbios_attributes,
 	.is_visible = smbios_instance_string_exist,
 };
···
 	NULL,
 };
 
-static struct attribute_group acpi_attr_group = {
+static const struct attribute_group acpi_attr_group = {
 	.attrs = acpi_attributes,
 	.is_visible = acpi_index_string_exist,
 };