dt: bindings: media: xilinx: sdirxss : Add clock framework support

dt: bindings: media: xilinx: sdirxss : Add clock framework support

The SDI Rx Subystem requires 3 clocks namely s_axi_aclk
(AXI lite interface clock), sdi_rx_clk (SMPTE SDI Rx core clock)
and video_out_clk (Video Output clock).
This patch adds the clocks and clock-names property to the
documentation.

Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>