spl: Use CONFIG_SPL... instead of CONFIG_..._SPL_...

We like to put the SPL first so it is clear that it relates to SPL. Rename
various malloc-related options which have crept in, to stick to this
convention.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Martyn Welch <martyn.welch@collabora.com>
Reviewed-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/configs/iot2050_defconfig b/configs/iot2050_defconfig
index a43a165..3cc0154 100644
--- a/configs/iot2050_defconfig
+++ b/configs/iot2050_defconfig
@@ -48,8 +48,8 @@
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SPL_STACK_R=y
-CONFIG_SYS_SPL_MALLOC=y
-CONFIG_SYS_SPL_MALLOC_SIZE=0x800000
+CONFIG_SPL_SYS_MALLOC=y
+CONFIG_SPL_SYS_MALLOC_SIZE=0x800000
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x1400
 CONFIG_SPL_DM_MAILBOX=y