arm: convert am3517_crane and am3517_evm to generic boards

Add CONFIG_SYS_GENERIC_BOARD to board's config header.

Boot-tested on am3517_evm board.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
diff --git a/include/configs/am3517_evm.h b/include/configs/am3517_evm.h
index e5b4621..b90a60d 100644
--- a/include/configs/am3517_evm.h
+++ b/include/configs/am3517_evm.h
@@ -19,6 +19,7 @@
 #define CONFIG_OMAP		1	/* in a TI OMAP core */
 #define CONFIG_OMAP3_AM3517EVM	1	/* working with AM3517EVM */
 #define CONFIG_OMAP_COMMON
+#define CONFIG_SYS_GENERIC_BOARD
 /* Common ARM Erratas */
 #define CONFIG_ARM_ERRATA_454179
 #define CONFIG_ARM_ERRATA_430973