Remove '=' from 'if CONFIG_XEN_CTRL_INTERFACE_VERSION <= 41500'. Because xendevicemodel_set_irq_level() was introduced in 4.15 version. Also, update xendevicemodel_set_irq_level() to return -1 for older versions. Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>