syslinux: improve isohybrid to process extra sector count for ISO 9660 image

syslinux: improve isohybrid to process extra sector count for ISO 9660 image

Due to commit [cdrtools-native: fix booting EFI ISO live failed]
applied to improve mkisofs to fix nsectors exceeds 0xffff situation
which set selection criteria type = 2 and save extra nsectors to
vendor unique selection criteria

In following case, add 64MB extra space to bootable image efi.img,
and the partition table of EFI is truncated to 32M

$ echo 'IMAGE_FSTYPES:pn-core-image-minimal = " live"' >> conf/local.conf
$ echo 'MACHINE_FEATURES:append = " efi pcbios"' >> conf/local.conf
$ echo '# 64MB extra space to bootable image efi.img' >> conf/local.conf
$ echo 'BOOTIMG_EXTRA_SPACE = "65535"' >> conf/local.conf
$ bitbake core-image-minimal
$ fdisk -l tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso
...
Device                                                                 Boot Start    End Sectors  Size Id Type
tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso1 *        0 376831  376832  184M  0 Empty
tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso2        120  65654   65535   32M ef EFI (FAT-12/16/32)

After applying this patch to process extra sector count, the partition
table of EFI is 90.3M

$ fdisk -l tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso
...
Device                                                                 Boot Start    End Sectors  Size Id Type
tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso1 *        0 376831  376832  184M  0 Empty
tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.rootfs.iso2        120 185151  185032 90.3M ef EFI (FAT-12/16/32)

[1]https://pdos.csail.mit.edu/6.828/2017/readings/boot-cdrom.pdf

(From OE-Core rev: b4e112ed7e6ba5a6c6df530d696485a588831851)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>