Add kernel removing instructions before installing KMD

[wangkl2]

After installing the new OEM kernel 5.14.0-1047-oem, there might be several Linux kernels and dkms might build the KMD on each of them, not only on the boot kernel, while there exists lots of Linux kernels versions that are not supported to build on. To avoid the error of "Error! Bad return status for module build on kernel:xxx", before installing the KMD, I recommend that the kernel removing instructions should be added.

Steps:
(1) Use the following command to list all the Linux kernel packages that have been installed.
$ dpkg --get-selections |grep linux
(2) Remove all the Linux kernel packages except for the packages for OEM kernel 5.14.0-1047-oem
$ sudo apt autoremove linux-headers-xxx linux-hwe-xxx-headers-xxx linux-image-xxx linux-modules-xxx
(3) $sudo reboot