net: ipa: sequencer type is for TX endpoints only

We only program the sequencer type for TX endpoints.  So move the
definition of the sequencer type fields into the TX-specific portion
of the endpoint configuration data.  There's no need to maintain
this in the IPA structure; we can extract it from the configuration
data it points to in the one spot it's needed.

We previously specified the sequencer type for RX endpoints with
INVALID values.  These are no longer needed, so get rid of them.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>