phy: xilinx: phy-zynqmp: mention SGMII as supported protocol

SGMII is validated on kria KR260 robotics starter kit. So modify the
comment description to include it in supported controllers list.

Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/1679940407-13131-1-git-send-email-radhey.shyam.pandey@amd.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>