ARM: at91: change name template in AT91_SOC_START macro

New devices are no more prefixed with at91 so remove the at91 and _name
concatenation.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>