Driver core: fix driver_register() return value

In this patch:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=16dc42e018c2868211b4928f20a957c0c216126c
the check was added for another driver to already claim the same device
on the same bus. But the returned error code was wrong: to modprobe, the
-EEXIST means that _this_ driver is already installed. It therefore
doesn't produce the needed error message when _another_ driver is trying
to register for the same device.  Returning -EBUSY fixes the problem.
Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/driver.c

@@ -236,7 +236,7 @@ int driver_register(struct device_driver *drv)
 		put_driver(other);
 		printk(KERN_ERR "Error: Driver '%s' is already registered, "
 			"aborting...\n", drv->name);
-		return -EEXIST;
+		return -EBUSY;
 	}
 
 	ret = bus_add_driver(drv);