libbootimg: Fix support of Stock Sony ELF boot images

 * Unlike all boot images built for CyanogenMod or AOSP based
    ROMs over the last years, the elf bootimages from Stock
    also include additional metadata in the header section
    that is required for the device to power up with its kernel

 * Add a 3900 8bits array at the end of the header,
    followed by the 16 chars of the added bootimage name,
    in order to match the Sony ELF 4096 first block
    and therefore save the additional data from Stock images

 * Regular Sony ELF images have about 1200-1600 chars there
    so filling the 4096 block is more than enough for this,
    and moving the bootimage name at the end makes things safer

Change-Id: Ic2b619b6f5e862920dcfefa5b86b016987305d4a
Signed-off-by: AdrianDC <radian.dc@gmail.com>

Author: AdrianDC

include/boot_img_hdr.h

@@ -130,6 +130,7 @@ struct boot_img_hdr_elf
     uint32_t cmd_msize;             /* cmdline size duplicate */
     uint32_t cmd_flags;             /* cmdline flags (0xAC to 0xAF) */
     uint32_t cmd_align;             /* cmdline alignment */
+    uint8_t header_vals[3900];      /* header additional values */
     uint8_t name[BOOT_NAME_SIZE];   /* added - asciiz product name */
 };