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/khadas-vim_defconfig b/configs/khadas-vim_defconfig
index 103ef54..5565635 100644
--- a/configs/khadas-vim_defconfig
+++ b/configs/khadas-vim_defconfig
@@ -10,6 +10,7 @@
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_IDENT_STRING=" khadas-vim"
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x1000000
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_CONSOLE_MUX=y
 # CONFIG_DISPLAY_CPUINFO is not set