dt-bindings: net: bluetooth: convert MT7622 Bluetooth to the json-schema

This helps validating DTS files. Introduced changes:
1. Dropped serial details from example
2. Added required example include

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>