The SWX pipeline instructions work with operands of different types:
header fields (h.header.field), packet meta-data (m.field), extern
object mailbox field (e.obj.field), extern function (f.field), action
data read from table entries (t.field), or immediate values; hence the
HMEFTI acronym.
For some pipeline instructions (add/sub, srl/shr, jmplt/jmpgt), only
the H, M and I cases were handled, while the E, F and T cases were
disregarded. This is what we fix here.