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/imx28_xea_defconfig b/configs/imx28_xea_defconfig
index cef7352..c1b0487 100644
--- a/configs/imx28_xea_defconfig
+++ b/configs/imx28_xea_defconfig
@@ -51,7 +51,7 @@
 CONFIG_SPL_MMC_TINY=y
 CONFIG_SPL_DM_SPI_FLASH=y
 CONFIG_SPL_OS_BOOT=y
-CONFIG_SYS_SPL_ARGS_ADDR=0x44000000
+CONFIG_SPL_PAYLOAD_ARGS_ADDR=0x44000000
 CONFIG_SPL_FALCON_BOOT_MMCSD=y
 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR=0x800
 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR=0x400