Adding the cp requirement for kmod images documentation.

It is not currently mentioned in the documentation that the minimal
reuirement for the kmod images are to have the `cp` binary present in the
image.

Signed-off-by: Yoni Bettan <[email protected]>

Author: ybettan

docs/mkdocs/documentation/kmod_image.md

@@ -11,6 +11,9 @@ Where:
 - `<prefix>` should be equal to `/opt` in most cases, as it is the `Module` CRD's default value;
 - `kernel-version` must be non-empty and equal to the kernel version the kernel modules were built for.
 
+In addition, the kmod image also reuired the `cp` binary to be present as the kmods will be copied from this
+image to the image-loader worker pod created by the operator.
+
 ## `depmod`
 
 It is recommended to run `depmod` at the end of the build process to generate `modules.dep` and map files.