Convert CONFIG_SPL_PAD_TO et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_PAD_TO
   CONFIG_SPL_MAX_SIZE
   CONFIG_TPL_PAD_TO
   CONFIG_TPL_MAX_SIZE

Note that we need to make TPL_MAX_SIZE be hex, and so move and convert the
existing places.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/imx8mn_bsh_smm_s2_defconfig b/configs/imx8mn_bsh_smm_s2_defconfig
index 69ba137..1a4db33 100644
--- a/configs/imx8mn_bsh_smm_s2_defconfig
+++ b/configs/imx8mn_bsh_smm_s2_defconfig
@@ -26,6 +26,7 @@
 CONFIG_DEFAULT_FDT_FILE="freescale/imx8mn-bsh-smm-s2.dtb"
 CONFIG_ARCH_MISC_INIT=y
 CONFIG_BOARD_LATE_INIT=y
+CONFIG_SPL_MAX_SIZE=0x25000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_BOOTROM_SUPPORT=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR=y