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/stm32mp15_dhcom_basic_defconfig b/configs/stm32mp15_dhcom_basic_defconfig
index a21fc92..bfa2008 100644
--- a/configs/stm32mp15_dhcom_basic_defconfig
+++ b/configs/stm32mp15_dhcom_basic_defconfig
@@ -15,6 +15,7 @@
 CONFIG_SPL_SPI_SUPPORT=y
 # CONFIG_ARMV7_VIRT is not set
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0xc2000000
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT=y
 CONFIG_SPL_FIT_SOURCE="board/dhelectronics/dh_stm32mp1/u-boot-dhcom.its"