The tool chain comes along with its own Linux kernel 3.x in your case and patching this kernel is not a good idea, as this can be shared among multiple projects which use Petalinux.
As asked in your question you have to replace the kernel with older kernel,
Xilinx maintains its kernel repo where you can find appropriate tags Refer Linux-xlnx
To add any particular kernel into Petalinux project,
Refer Zynq TRD Section 5.3 : Add Linux kernel 3.14 support
OR you can make select the
petalinux-config :: "Linux Component Selection" > "Remote" >
(Fill your Linux-xlnx GIT repo path with tag)
But be cautious last will download the kernel every time when you delete the 'build' directory.
Good Luck !!