atmel: at91sam9x5: add spi flash boot support

Add at91sam9x5 series spi flash boot support

Using at91sam9x5ek_spiflash to configure, then it can boot from at25df321
serial flash

SPI mater work in 30Mhz speed, while not 1Mhz speed. This will base on
atmel_spi patch, or else, it will occur receive overrun

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/boards.cfg b/boards.cfg
index ef08dbe..72e7803 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -96,6 +96,7 @@
 at91sam9rlek_dataflash       arm         arm926ejs   at91sam9rlek        atmel          at91        at91sam9rlek:AT91SAM9RL,SYS_USE_DATAFLASH
 at91sam9rlek_nandflash       arm         arm926ejs   at91sam9rlek        atmel          at91        at91sam9rlek:AT91SAM9RL,SYS_USE_NANDFLASH
 at91sam9x5ek_nandflash       arm         arm926ejs   at91sam9x5ek        atmel          at91        at91sam9x5ek:AT91SAM9X5,SYS_USE_NANDFLASH
+at91sam9x5ek_spiflash        arm         arm926ejs   at91sam9x5ek        atmel          at91        at91sam9x5ek:AT91SAM9X5,SYS_USE_SPIFLASH
 at91sam9xeek_dataflash_cs0   arm         arm926ejs   at91sam9260ek       atmel          at91        at91sam9260ek:AT91SAM9XE,SYS_USE_DATAFLASH_CS0
 at91sam9xeek_dataflash_cs1   arm         arm926ejs   at91sam9260ek       atmel          at91        at91sam9260ek:AT91SAM9XE,SYS_USE_DATAFLASH_CS1
 at91sam9xeek_nandflash       arm         arm926ejs   at91sam9260ek       atmel          at91        at91sam9260ek:AT91SAM9XE,SYS_USE_NANDFLASH