Bluetooth: btintel: Functions to send firmware header / payload

New generation controllers supports ECDSA secure boot engine.
This patch adds,

1) function to send ECDSA header

2) function to download complete firmware for new generation Intel
   controllers

Signed-off-by: Kiran K <kiran.k@intel.com>
Signed-off-by: Amit K Bag <amit.k.bag@intel.com>
Signed-off-by: Raghuram Hegde <raghuram.hegde@intel.com>
Reviewed-by: Chethan T N <chethan.tumkur.narayan@intel.com>
Reviewed-by: Srivatsa Ravishankar <ravishankar.srivatsa@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>