ARM: at91: fix and update README.at91 document

This patch implement following things
  - The link no longer accessable
  - Remove the error configuration command
  - Update soldered data flash memory map
  - Update at91sam9m10g45ek memory size to 128MiB

Signed-off-by: Bo Shen <voice.shen@atmel.com>
ARM: at91: add at91sam9x5 and sama5d3x information

This patch add following EK information
  - at91sam9x5ek
  - sama5d3xek

Signed-off-by: Bo Shen <voice.shen@atmel.com>
ARM: at91: add NAND partition table and index

Add NAND partition table, EK board support boot up NAND flash using
the same NAND partition table

Add Index in this file

Signed-off-by: Bo Shen <voice.shen@atmel.com>