Also remove the 0xff comparison when validating the bootloader
message fields. As the fields won't be erased to 0xff after we
remove the MTD support.
Bug: 28202046
Test: The recovery folder compiles for aosp_x86-eng
Change-Id: Ibb30ea1b2b28676fb08c7e92a1e5f7b6ef3247ab
(cherry picked from commit 7aa88748f6)
bootloader_messages merges bootloader_message_writer
and bootloader.cpp, so we can use the same library to
manage bootloader_message in normal boot and recovery mode.
Bug: 29582118
Change-Id: I9efdf776ef8f02b53911ff43a518e035e0c29618