Requirements when C<5, Dimensionality = 0 and Throughput > 1

## Background

https://abs-tudelft.github.io/tydi/specification/physical.html#signal-omission

Specifies that:
* `stai` is contingent on C≥6∧N>1
* `endi` is contingent on (C≥5∨D≥1)∧N>1
* `strb` is contingent on C≥7∨D≥1

## Potential Issue

As a result of these requirements, a Stream with C<5, D=0 and element lanes N>1 should not have an `endi` signal.
This means that all lanes in a transfer _must_ be valid, as there is no way to set individual lanes as being inactive.

## Suggested Fix

The current specification implies that any transfer with C<5, D=0, N>1 must consist of Q elements where `Q mod N = 0`.

It is not clear whether this is intentional, I can think of two other ways in which to make behavior consistent:
1. N>1 is contingent on D>0∨C≥5 - i.e., it is not allowed to transfer multiple elements at the same time except in a list or at higher complexities.
2. `endi` is solely contingent on N>1 - i.e., it is always allowed to transfer multiple elements, and `endi` can be used to encode lane validity when sequences do not align to the number of element lanes.