rocker: introduce rocker_dma_desc_cookie_ptr_[sg]et helpers

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
rocker: use desc cookie to store pointer to skb

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
rocker: introduce rocker_wait_* helpers and use them in hw test functions

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
rocker: use rocker_wait_* helpers for cmd and store wait in desc cookie

Signed-off-by: Jiri Pirko <jiri@resnulli.us>