In preparation to the introduction of the support for other
bootloaders than Grub, this commit switches from having the iso9660
support "select" the necessary bootloader to using a "depends on".
The main motivation is that the isolinux bootloader support will
really need to do a "depends on", due to the need of having a certain
option enabled, but this option being a kconfig "choice".
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>