CONFIG_ARCH_P720T is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

P720T

modulename: p720t.ko

and/or

board-p720t.ko

configname: CONFIG_ARCH_P720T

Linux Kernel Configuration
└─>CLPS711X/EP721X Implementations
└─>P720T
In linux kernel since version 2.6.12  
Say Y here if you intend to run this kernel on the ARM Prospector
720T.

source code:
arch/arm/mach-clps711x/p720t.c