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/km_kirkwood_pci_defconfig b/configs/km_kirkwood_pci_defconfig
index 249b42f..250f2cc 100644
--- a/configs/km_kirkwood_pci_defconfig
+++ b/configs/km_kirkwood_pci_defconfig
@@ -11,6 +11,7 @@
 CONFIG_BOOTCOUNT_BOOTLIMIT=3
 CONFIG_ENV_OFFSET_REDUND=0x2000
 CONFIG_IDENT_STRING="\nHitachi Power Grids Kirkwood PCI"
+CONFIG_SYS_LOAD_ADDR=0x800000
 CONFIG_SYS_EXTRA_OPTIONS="KM_KIRKWOOD_PCI"
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Hit <SPACE> key to stop autoboot in %2ds\n"