Bluetooth: btintel_pcie: treat boot stage bit 12 as warning

Bluetooth: btintel_pcie: treat boot stage bit 12 as warning

CSR boot stage register bit 12 is documented as a device warning,
not a fatal error. Rename the bit definition accordingly and stop
including it in btintel_pcie_in_error().

This keeps warning-only boot stage values from being classified as
errors while preserving abort-handler state as the actual error
condition.

Fixes: 190377500fde ("Bluetooth: btintel_pcie: Dump debug registers on error")
Signed-off-by: Kiran K <kiran.k@intel.com>
Signed-off-by: Sai Teja Aluvala <aluvala.sai.teja@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>