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/common/spl/spl_ubi.c b/common/spl/spl_ubi.c
index bcac25c..d7ab9ef 100644
--- a/common/spl/spl_ubi.c
+++ b/common/spl/spl_ubi.c
@@ -50,7 +50,7 @@
 		volumes[0].vol_id = CONFIG_SPL_UBI_LOAD_KERNEL_ID;
 		volumes[0].load_addr = (void *)CONFIG_SYS_LOAD_ADDR;
 		volumes[1].vol_id = CONFIG_SPL_UBI_LOAD_ARGS_ID;
-		volumes[1].load_addr = (void *)CONFIG_SYS_SPL_ARGS_ADDR;
+		volumes[1].load_addr = (void *)CONFIG_SPL_PAYLOAD_ARGS_ADDR;
 
 		ret = ubispl_load_volumes(&info, volumes, 2);
 		if (!ret) {