Add Bootloader Assert

Per cyanogen, users on older bootloader/basebands are prone to
adverse behavior in respect to recent commits for the device.

Add assert to alert user to begin firmware update process manually.

Change-Id: I332a5cd81a8ecf4a28fd278d448bb1a9a6c44158
hammerhead: Remove deprecated flag

Change-Id: Id52576dd2262eca00292a90511245445dab2ae08