ARM: at91: add at91sam9x5 and sama5d3x information

This patch add following EK information
  - at91sam9n12ek, at91sam9x5ek
  - sama5d3xek

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

doc/README.at91

@@ -102,6 +102,48 @@ Environment variables
 	You can choose your storage location at config step (here for at91sam9rlek) :
 		make at91sam9rlek_nandflash_config	- use nand flash
 
+
+------------------------------------------------------------------------------
+AT91SAM9N12EK, AT91SAM9X5EK
+------------------------------------------------------------------------------
+
+Memory map
+	0x20000000 - 27FFFFFF	SDRAM (128 MB)
+
+Environment variables
+
+	U-Boot environment variables can be stored at different places:
+		- Nand flash.
+		- SD/MMC card
+		- Serialflash/Dataflash on SPI chip select 0
+
+	You can choose your storage location at config step (here for at91sam9x5ek) :
+		make at91sam9x5ek_dataflash_config	- use data flash
+		make at91sam9x5ek_mmc_config		- use sd/mmc card
+		make at91sam9x5ek_nandflash_config	- use nand flash
+		make at91sam9x5ek_spiflash_config	- use serial flash
+
+
+------------------------------------------------------------------------------
+SAMA5D3XEK
+------------------------------------------------------------------------------
+
+Memory map
+	0x20000000 - 3FFFFFFF	SDRAM (512 MB)
+
+Environment variables
+
+	U-Boot environment variables can be stored at different places:
+		- Nand flash.
+		- SD/MMC card
+		- Serialflash on SPI chip select 0
+
+	You can choose your storage location at config step (here for sama5d3xek) :
+		make sama5d3xek_mmc_config		- use SD/MMC card
+		make sama5d3xek_nandflash_config	- use nand flash
+		make sama5d3xek_serialflash_config	- use serial flash
+
+
 II. Watchdog support
 
 	For security reasons, the at91 watchdog is running at boot time and,