Bluetooth: Keep track of UUID type upon addition

The primary purpose of the UUIDs is to enable generation of EIR and AD
data. In these data formats the UUIDs are split into separate fields
based on whether they're 16, 32 or 128 bit UUIDs. To make the generation
of these data fields simpler this patch adds a type member to the
bt_uuid struct and assigns a value to it as soon as the UUID is added to
the kernel. This way the type doesn't need to be calculated each time
the UUID list is later iterated.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>