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/at91sam9g10ek_nandflash_defconfig b/configs/at91sam9g10ek_nandflash_defconfig
index 414e41b..fff8ee9 100644
--- a/configs/at91sam9g10ek_nandflash_defconfig
+++ b/configs/at91sam9g10ek_nandflash_defconfig
@@ -11,6 +11,7 @@
 CONFIG_DEBUG_UART_CLOCK=100000000
 CONFIG_ENV_OFFSET_REDUND=0x100000
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x22000000
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9G10,SYS_USE_NANDFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y