iot_dk: Link for eFlash

That's what we'll have in production.
But note it won't work for loading via JTAG as
eFlash is not directly writable, one needs to use
prebootloader to flash uboot.bin from SD-card into eFlash.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

configs/iot_devkit_defconfig

@@ -4,7 +4,7 @@ CONFIG_CPU_ARCEM6=y
 CONFIG_SYS_ICACHE_OFF=y
 CONFIG_SYS_DCACHE_OFF=y
 CONFIG_TARGET_IOT_DEVKIT=y
-CONFIG_SYS_TEXT_BASE=0x20000000
+CONFIG_SYS_TEXT_BASE=0x00000000
 CONFIG_SYS_CLK_FREQ=16000000
 CONFIG_LOCALVERSION="-iotdk-1.0"
 # CONFIG_ARCH_FIXUP_FDT_MEMORY is not set