Bluetooth: btintel: read ROM debug registers on FW download failure

The bootloader records init sequence progress and debug info in four
core debug registers, useful for debugging FW download failures.

Add btintel_get_rom_debug_info() to issue BTINTEL_GET_ROM_DEBUG_INFO
(0xfcde) and log these registers, and invoke it from every FW download
failure and timeout path: btintel_download_fw() (legacy .sfi flow) and
btintel_prepare_fw_download_tlv() (TLV flow), before resetting to the
bootloader.

Tested by corrupting the operational firmware file to force a
download timeout; the driver logged the debug registers on each
failure and retry, e.g.:

  Bluetooth: hci0: Firmware loading timeout
  Bluetooth: Intel get rom debug info: dr0:0x80000001 dr1:0x00000000 dr2:0x00000001 dr3:0x00df0071

Signed-off-by: Ravindra <ravindra@intel.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>