ARM: zynq: Fix incorrect reference to XM013 instead of XM011

Fix comment about targeted extension card. It was likely just c&p error.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/39e16e667aa8f132496092d4fa554935ddd5a55f.1606399500.git.michal.simek@xilinx.com