fs/iso9660: install Isolinux comboot modules

This installs every module selected by the BR2_TARGET_SYSLINUX_C32.
This is useful when using a custom Isolinux configuration file that may use
comboot modules.

Signed-off-by: Noé Rubinstein <nrubinstein@aldebaran.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>