Staging: lustre: obdclass: class_obd: Declare as static

Declare class_resolve_dev_name as static it is not used anywhere
apart from this particular file.Also remove the declaration
from header file

Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>