android: boot: support boot image header version 3 and 4

Enable the support for boot image header version 3 and 4
using abootimg command.

In order to use version 3 or 4:

1- Vendor boot image address should be given to abootimg cmd.

	abootimg addr $1 $vendor_boot_load_addr

2- "ramdisk_addr_r" env variable (ramdisk address) should be set to host
the ramdisk : generic ramdisk + vendor ramdisk

Replace "struct andr_boot_img_hdr_v0*" by "void *" in
some functions since v3 and v4 are now supported as well.

Signed-off-by: Safae Ouajih <souajih@baylibre.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>