[yocto] Thud Kernel Configuration not Working

[nick]

Greetings,
I was trying to build a kernel with these files in a new layer for no smp to be enabled but have no
idea why it doesn't work. This is after looking at the kernel manual and it's literally the same
files excluding the disabling of smp as the chosen option.

.cfg for kernel option is called smp.cfg and this the file's content:
#Disable SMP
CONFIG_SMP=n

This is my bbappend called linux-yocto-4.1.8.bbappend:
 # Include kernel configuration fragment
 FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
 SRC_URL += "file://smp.cfg"

If anyone has ideas thanks in advance,

Nick