Bluetooth: btintel: Add manufacturing enter/exit helpers

Older Intel controllers need to enter manufacturing mode to perform
some vendor specific operations (patching, configuration...).
Add enter/exit manufaturing methods and refactor existing
manufacturing code.
Exit can be configured to perform a reset. Reset can be performed
either with patches activated or deactivated.

Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>