driver core: Remove unnecessary is_fwnode_dev variable in device_add()

That variable is no longer necessary. Remove it and also fix a minor
typo in comments.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200520034824.79049-2-saravanak@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>