Please look at recommendations below how to change the kernel configuration
through menuconfig
$ bitbake -c menuconfig linux-imx
This creates a config file in (as an example)
tmp/work/imx6qsabresd-poky-linux-gnueabi/linux-imx/3.0.35-r33.10/git/.config
This file should be copied to the defconfig location in order to set the changes.
Below is an example of the devconfig location :
meta-fsl-arm/recipes-kernel/linux/linux-imx-3.0.35/mx6
Then use the commands.
$ bitbake -c cleansstate linux-imx
$ bitbake linux-imx
As for configuring the kernel more details are available on the following community document:
https://community.freescale.com/docs/DOC-95045
Regards,
Yuri.