CONFIG_SH_DREAMCAST is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

Dreamcast

modulename: dma-pvr2.ko

and/or

ops-dreamcast.ko

configname: CONFIG_SH_DREAMCAST

Linux/SuperH Kernel Configuration
└─>System type
└─>Board support
└─>Dreamcast
In linux kernel since version 2.6.12  
Select Dreamcast if configuring for a SEGA Dreamcast.
More information at <http://www.linux-sh.org>

source code:
/arch/sh/drivers/dma/