tam3517: fix NAND detection

commit a0a37183bd7 "ARM: omap: merge GPMC initialization code for
all platform" needs CONFIG_NOR, CONFIG_NAND or CONFIG_CMD_ONENAND
to be set to access flash. Add CONFIG_NAND for tam3517 derived
boards to prevent the following error: "nand: error: Unable to
find NAND settings in GPMC Configuration - quitting"

cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>

include/configs/tam3517-common.h

@@ -185,6 +185,7 @@
 /* Configure the PISMO */
 #define PISMO1_NAND_SIZE		GPMC_SIZE_128M
 
+#define CONFIG_NAND
 #define CONFIG_NAND_OMAP_GPMC
 #define CONFIG_ENV_IS_IN_NAND
 #define SMNAND_ENV_OFFSET		0x180000 /* environment starts here */