board: sysam: stmark2: add missing environment location

Signed-off-by: Angelo Dureghello <angelo@sysam.it>
diff --git a/configs/stmark2_defconfig b/configs/stmark2_defconfig
index ffb8af9..7071982 100644
--- a/configs/stmark2_defconfig
+++ b/configs/stmark2_defconfig
@@ -21,6 +21,7 @@
 CONFIG_CMD_MTDPARTS=y
 CONFIG_MTDIDS_DEFAULT="nor0=spi-flash.0"
 CONFIG_MTDPARTS_DEFAULT="mtdparts=spi-flash.0:1m(u-boot),7m(kernel),-(rootfs)"
+CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_MTD=y
 CONFIG_REGEX=y