net: ipa: define all IPA status mask bits

There is a 16 bit status mask defined in the IPA packet status
structure, of which only one (TAG_VALID) is currently used.

Define all other IPA status mask values in an enumerated type whose
numeric values are bit mask values (in CPU byte order) in the status
mask.  Use the TAG_VALID value from that type rather than defining a
separate field mask.

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