CONFIG_ARCH_LPC18XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

NXP LPC18xx/LPC43xx

modulename: clk-lpc18xx-cgu.ko

and/or

clk-lpc18xx-ccu.ko

and/or

clk-lpc18xx-creg.ko

configname: CONFIG_ARCH_LPC18XX

Linux Kernel Configuration
└─>System Type
└─>NXP LPC18xx/LPC43xx
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Support for NXP's LPC18xx Cortex-M3 and LPC43xx Cortex-M4
high performance microcontrollers.

source code:
drivers/clk/nxp/clk-lpc18xx-cgu.c