Moved declaration of gBootDevice into its own header.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@15518 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/fs/devfs.cpp

@@ -14,6 +14,7 @@
 #include <pnp_devfs.h>
 #include <NodeMonitor.h>
 
+#include <boot_device.h>
 #include <kdevice_manager.h>
 #include <KPath.h>
 #include <vfs.h>
@@ -136,9 +137,6 @@ static status_t publish_device(struct devfs *fs, const char *path,
 					driver_entry *driver, device_hooks *ops);
 
 
-// The boot device, if already present
-extern dev_t gBootDevice;
-
 /* the one and only allowed devfs instance */
 static struct devfs *sDeviceFileSystem = NULL;