spl: Rename SYS_SPL_ARGS_ADDR to SPL_PAYLOAD_ARGS_ADDR

Rename this so that SPL is first, as per U-Boot convention. Also add
PAYLOAD_ since this is where in memory the parameters for the payload
have been stored.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/stm32f746-disco_spl_defconfig b/configs/stm32f746-disco_spl_defconfig
index 1b8b5a1..b2a7861 100644
--- a/configs/stm32f746-disco_spl_defconfig
+++ b/configs/stm32f746-disco_spl_defconfig
@@ -36,7 +36,7 @@
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SPL_MTD_SUPPORT=y
 CONFIG_SPL_XIP_SUPPORT=y
-CONFIG_SYS_SPL_ARGS_ADDR=0x80c0000
+CONFIG_SPL_PAYLOAD_ARGS_ADDR=0x80c0000
 CONFIG_SPL_DM_RESET=y
 CONFIG_SYS_PROMPT="U-Boot > "
 CONFIG_SYS_PBSIZE=1050