Turn on -Werror for recovery

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
diff --git a/recovery.cpp b/recovery.cpp
index 91c18b5..12df61d 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -306,12 +306,12 @@
     get_bootloader_message(&boot);  // this may fail, leaving a zeroed structure
     stage = strndup(boot.stage, sizeof(boot.stage));
 
-    if (boot.command[0] != 0 && boot.command[0] != 255) {
+    if (boot.command[0] != 0) {
         std::string boot_command = std::string(boot.command, sizeof(boot.command));
         LOG(INFO) << "Boot command: " << boot_command;
     }
 
-    if (boot.status[0] != 0 && boot.status[0] != 255) {
+    if (boot.status[0] != 0) {
         std::string boot_status = std::string(boot.status, sizeof(boot.status));
         LOG(INFO) << "Boot status: " << boot_status;
     }
@@ -328,7 +328,7 @@
                 (*argv)[*argc] = strdup(arg);
             }
             LOG(INFO) << "Got arguments from boot message";
-        } else if (boot.recovery[0] != 0 && boot.recovery[0] != 255) {
+        } else if (boot.recovery[0] != 0) {
             std::string boot_recovery = std::string(boot.recovery, 20);
             LOG(ERROR) << "Bad boot message\n" << "\"" <<boot_recovery << "\"";
         }