Convert CONFIG_SYS_LOAD_ADDR to Kconfig

Now that we have consistent usage, migrate this symbol to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/configs/vf610twr_nand_defconfig b/configs/vf610twr_nand_defconfig
index 0cd9cb7..37731d6 100644
--- a/configs/vf610twr_nand_defconfig
+++ b/configs/vf610twr_nand_defconfig
@@ -11,6 +11,7 @@
 CONFIG_SYS_I2C_MXC_I2C2=y
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="vf610-twr"
+CONFIG_SYS_LOAD_ADDR=0x82000000
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/vf610twr/imximage.cfg"
 CONFIG_BOOTDELAY=3
 CONFIG_LOGLEVEL=3