PCI: Constify sysfs 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
   8480	   2024	      4	  10508	   290c	drivers/pci/pci-sysfs.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
   8736	   1768	      4	  10508	   290c	drivers/pci/pci-sysfs.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci-sysfs.c

@@ -1735,7 +1735,7 @@ const struct attribute_group *pcie_dev_groups[] = {
 	NULL,
 };
 
-static struct attribute_group pci_dev_hp_attr_group = {
+static const struct attribute_group pci_dev_hp_attr_group = {
 	.attrs = pci_dev_hp_attrs,
 	.is_visible = pci_dev_hp_attrs_are_visible,
 };
@@ -1759,23 +1759,23 @@ static umode_t sriov_attrs_are_visible(struct kobject *kobj,
 	return a->mode;
 }
 
-static struct attribute_group sriov_dev_attr_group = {
+static const struct attribute_group sriov_dev_attr_group = {
 	.attrs = sriov_dev_attrs,
 	.is_visible = sriov_attrs_are_visible,
 };
 #endif /* CONFIG_PCI_IOV */
 
-static struct attribute_group pci_dev_attr_group = {
+static const struct attribute_group pci_dev_attr_group = {
 	.attrs = pci_dev_dev_attrs,
 	.is_visible = pci_dev_attrs_are_visible,
 };
 
-static struct attribute_group pci_bridge_attr_group = {
+static const struct attribute_group pci_bridge_attr_group = {
 	.attrs = pci_bridge_attrs,
 	.is_visible = pci_bridge_attrs_are_visible,
 };
 
-static struct attribute_group pcie_dev_attr_group = {
+static const struct attribute_group pcie_dev_attr_group = {
 	.attrs = pcie_dev_attrs,
 	.is_visible = pcie_dev_attrs_are_visible,
 };