net: ipa: program upper nibbles of sequencer type

The upper two nibbles of the sequencer type were not used for
SDM845, and were assumed to be 0.  But for SC7180 they are used, and
so they must be programmed by ipa_endpoint_init_seq().  Fix this bug.

IPA_SEQ_PKT_PROCESS_NO_DEC_NO_UCP_DMAP doesn't have a descriptive
comment, so add one.

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