configs: k2*_evm: let each board decide env location

Not all TI Keystone2 EVMs want environment in NAND flash.
K2G EVM which has an MMC/SD slot, keep environment in a
FAT partition on SD card.

Since ti_armv7_keystone2.h defines environment is in NAND,
boards which do not follow that have to #undef'ine that
configuration. This leads to ugly ordering issues around
where exactly the include of ti_armv7_keystone2.h can come
in within the k2*_evm.h files.

Move environment location to config file of each board.
This should make it easy to change it for any one board
without affecting all other boards.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
diff --git a/include/configs/k2g_evm.h b/include/configs/k2g_evm.h
index bee1be7..9a07eac 100644
--- a/include/configs/k2g_evm.h
+++ b/include/configs/k2g_evm.h
@@ -63,8 +63,8 @@
 #define CONFIG_PHY_MICREL
 #define PHY_ANEG_TIMEOUT	10000 /* PHY needs longer aneg time */
 
-#undef CONFIG_ENV_IS_IN_NAND
 #define CONFIG_ENV_IS_IN_FAT
+#define CONFIG_ENV_SIZE			(256 << 10)  /* 256 KiB */
 #define FAT_ENV_INTERFACE		"mmc"
 #define FAT_ENV_DEVICE_AND_PART		"0:1"
 #define FAT_ENV_FILE			"uboot.env"