Revert "mkbootimg: add version and patch level"

This reverts commit 3edc43234a0c0d592bc67b61f39c45eed238cef2.

Bug: 27580174
Change-Id: I42dac32eb7a70498accf2b8b4fde1ed0d221ca0b
diff --git a/mkbootimg/bootimg.h b/mkbootimg/bootimg.h
index 2bd8230..5ab6195 100644
--- a/mkbootimg/bootimg.h
+++ b/mkbootimg/bootimg.h
@@ -43,11 +43,7 @@
 
     uint32_t tags_addr;    /* physical addr for kernel tags */
     uint32_t page_size;    /* flash page size we assume */
-
-    /* operating system version; "1.2.34" -> 010234 */
-    uint32_t os_version;
-    /* operating system patch level; "2016-01-01" -> 20160101 */
-    uint32_t os_patch_level;
+    uint32_t unused[2];    /* future expansion: should be 0 */
 
     uint8_t name[BOOT_NAME_SIZE]; /* asciiz product name */