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/brppt2_defconfig b/configs/brppt2_defconfig
index 51c1372..2a213cd 100644
--- a/configs/brppt2_defconfig
+++ b/configs/brppt2_defconfig
@@ -23,6 +23,7 @@
 CONFIG_SPL_SPI_SUPPORT=y
 # CONFIG_CMD_BMODE is not set
 # CONFIG_EXPERT is not set
+CONFIG_SYS_LOAD_ADDR=0x10700000
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/mach-imx/spl_sd.cfg"
 CONFIG_SPI_BOOT=y