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/taurus_defconfig b/configs/taurus_defconfig
index 80f75ce..dbaf288 100644
--- a/configs/taurus_defconfig
+++ b/configs/taurus_defconfig
@@ -26,6 +26,7 @@
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x22000000
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9G20,MACH_TYPE=2067"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y