tlv: Allow control over comprehension bit in COMPR_TLV_IE
This allows construction of a comprehension TLV with the bit set or
cleared. The default is comprehension=True to not break existing code.
```
>>> foo = Foo(decoded=b"2342", comprehension=True)
>>> bar = Foo(decoded=b"2342", comprehension=False)
```
Related: OS#6989
Change-Id: I9ca689b9b51152f3907ea470c7b42a0b12208459
