Convert CONFIG_STANDALONE_LOAD_ADDR to Kconfig

This converts the following to Kconfig:
   CONFIG_STANDALONE_LOAD_ADDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xtfpga_defconfig b/configs/xtfpga_defconfig
index f5eeea4..d3a350f 100644
--- a/configs/xtfpga_defconfig
+++ b/configs/xtfpga_defconfig
@@ -9,6 +9,7 @@
 CONFIG_ENV_ADDR=0xF7FE0000
 CONFIG_XTFPGA_KC705=y
 CONFIG_SYS_MONITOR_LEN=262144
+CONFIG_STANDALONE_LOAD_ADDR=0x00800000
 CONFIG_SYS_MONITOR_BASE=0xF6000000
 CONFIG_DYNAMIC_SYS_CLK_FREQ=y
 CONFIG_SHOW_BOOT_PROGRESS=y