devlink: collect flash notify params into a struct

The dev flash status notify function parameter lists are getting
rather long, so add a struct to be filled and passed rather than
continuously changing the function signatures.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>