dm: at91: Move snapper9260 to generic baord

This works correctly, so switch it over before the deadline.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/configs/snapper9260.h

@@ -20,6 +20,7 @@
 /* ARM asynchronous clock */
 #define CONFIG_SYS_AT91_MAIN_CLOCK	18432000 /* External Crystal, in Hz */
 #define CONFIG_SYS_AT91_SLOW_CLOCK	32768
+#define CONFIG_SYS_GENERIC_BOARD
 
 /* CPU */
 #define CONFIG_ARCH_CPU_INIT