add support for the at91sam9260 based board smartweb from
siemens. SPL is used without serial support, as this
SoC has only 4k sram for running SPL. Here a U-Boot
bootlog:

RomBOOT
>

U-Boot 2015.07-rc2-00109-g4ae828c (Jun 15 2015 - 09:31:16 +0200)

CPU: AT91SAM9260
Crystal frequency:   18.432 MHz
CPU clock        :  198.656 MHz
Master clock     :   99.328 MHz
       Watchdog enabled
DRAM:  64 MiB
WARNING: Caches not enabled
NAND:  256 MiB
In:    serial
Out:   serial
Err:   serial
Net:   macb0
Hit any key to stop autoboot:  0
U-Boot>

Signed-off-by: Heiko Schocher <hs@denx.de>