CONFIG_MPC830x_RDB is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Freescale MPC830x RDB and derivatives

modulename: mpc830x_rdb.ko

configname: CONFIG_MPC830x_RDB

Linux Kernel Configuration
└─>83xx-based boards
└─>Freescale MPC830x RDB and derivatives
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
This option enables support for the MPC8308 RDB and MPC8308 P1M boards.

source code: