zynq: Add zynq zed board support

zynq: Add zynq zed board support

Zed is a complete development board based on the
Xilinx Zynq-7000 All Programmable SoC.

APSOC:
- XC7Z020-CLG484-1
Memory:
- 512 MB DDR3
- 256 Mb Quad-SPI Flash(
- Full size SD/MMC card cage
Connectivity:
- 10/100/1000 Ethernet
- USB OTG (Device/Host/OTG)
- USB-UART
Expansion:
- FMC (Low Pin Count)
- Pmod. headers (2x6)
Video/Display:
- HDMI output (1080p60 + audio)
- VGA connector
- 128 x 32 OLED
- User LEDs (9)
User inputs:
- Slide switches (8)
- Push button switches (7)
Audio:
- 24-bit stereo audio CODEC
- Stereo line in/out
- Headphone
- Microphone input
Analog:
- Xilinx XADC header
- Supports 4 analog inputs
- 2 Differential / 4 Single-ended
Debug:
- On-board USB JTAG programming port
- ARM Debug Access Port (DAP)

For more info - http://zedboard.org/product/zedboard

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>