net: ipa: define remaining IPA status field values

Define the remaining values for opcode and exception fields in the
IPA packet status structure.  Most of these values are powers-of-2,
suggesting they are meant to be used as bitmasks, but that is not
the case.  Add comments to be clear about this, and express the
values in decimal format.

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