inquiry: refactor the code for unmarshalling periperal qualifier and device type

All inqury results have qualifier and device type in the first byte of the
data. So no need have decoding of this in each branch of the
what-type-of-inquire-data-is-this conditional.
We can start by always decode these two fields before we switch to doing
page specific decodes.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Merge pull request #10 from sahlberg/pqdt-inquiry

inquiry: refactor the code for unmarshalling periperal qualifier and dev...