CONFIG_PPC_MPC52xx is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

52xx-based boards

modulename: mpc5xxx_clocks.ko

configname: CONFIG_PPC_MPC52xx

Linux Kernel Configuration
└─>52xx-based boards
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
source code:
arch/powerpc/sysdev/mpc5xxx_clocks.c