rpi-userland: Fix vcfiled startup

The VideoCore file server daemon startup script installed from this package is
not compatible with BuildRoot (because of its naming and other Debian
dependencies), which prevented vcfiled from starting. Hence, prevent this
package from installing its vcfiled startup script, and add a configuration
option to install a vcfiled SysV init script suitable for BuildRoot.

[Peter: tweak help text as suggested by Yann]
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>