xilinx: Enable support for SquashFS

Enable SquashFS for all xilinx platforms.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/dbe85afda8cd90ebfc537979d382808ff9bec160.1655982259.git.michal.simek@amd.com