xen-pciback: Add name prefix to global 'permissive' variable

The variable for the 'permissive' module parameter used to be static
but was recently changed to be extern. This puts it in the kernel
global namespace if the driver is built-in, so its name should begin
with a prefix identifying the driver.

Signed-off-by: Ben Hutchings <[e-mail]>
Fixes: af6fc858a35b ("xen-pciback: limit guest control of command register")
Signed-off-by: David Vrabel <[e-mail]>

drivers/xen/xen-pciback/conf_space.c

···
 #include "conf_space.h"
 #include "conf_space_quirks.h"
 
-bool permissive;
-module_param(permissive, bool, 0644);
+bool xen_pcibk_permissive;
+module_param_named(permissive, xen_pcibk_permissive, bool, 0644);
 
 /* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
  * xen_pcibk_write_config_word, and xen_pcibk_write_config_byte are created. */
···
 		 * This means that some fields may still be read-only because
 		 * they have entries in the config_field list that intercept
 		 * the write and do nothing. */
-		if (dev_data->permissive || permissive) {
+		if (dev_data->permissive || xen_pcibk_permissive) {
 			switch (size) {
 			case 1:
 				err = pci_write_config_byte(dev, offset,

drivers/xen/xen-pciback/conf_space.h

···
 	void *data;
 };
 
-extern bool permissive;
+extern bool xen_pcibk_permissive;
 
 #define OFFSET(cfg_entry) ((cfg_entry)->base_offset+(cfg_entry)->field->offset)
 

drivers/xen/xen-pciback/conf_space_header.c

···
 
 	cmd->val = value;
 
-	if (!permissive && (!dev_data || !dev_data->permissive))
+	if (!xen_pcibk_permissive && (!dev_data || !dev_data->permissive))
 		return 0;
 
 	/* Only allow the guest to control certain bits. */