bnxt_en: Use direct API instead of indirection

For a single ULP user there is no need for complicating function
indirection calls. Remove all this complexity in favour of direct
function calls exported by the bnxt_en driver. This allows to
simplify the code greatly. Also remove unused ulp_async_notifier.

Suggested-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Reviewed-by: Selvin Xavier <selvin.xavier@broadcom.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>