x86/PCI: add spinlock held check to 'pcibios_fwaddrmap_lookup()'

'pcibios_fwaddrmap_lookup()' is used to maintain FW-assigned BIOS BAR
values for reinstatement when normal resource assignment attempts
fail and must be called with the 'pcibios_fwaddrmap_lock' spinlock
held.

This patch adds a WARN_ON notification if the spinlock is not currently
held by the caller.

Signed-off-by: Myron Stowe <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

arch/x86/pci/i386.c

···
 {
 	struct pcibios_fwaddrmap *map;
 
+	WARN_ON(!spin_is_locked(&pcibios_fwaddrmap_lock));
+
 	list_for_each_entry(map, &pcibios_fwaddrmappings, list)
 		if (map->dev == dev)
 			return map;