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/topic_miamilite_defconfig b/configs/topic_miamilite_defconfig
index 5acf1de..1e64b06 100644
--- a/configs/topic_miamilite_defconfig
+++ b/configs/topic_miamilite_defconfig
@@ -25,6 +25,7 @@
 CONFIG_BOOTCOMMAND="if mmcinfo; then if fatload mmc 0 0x1900000 ${bootscript}; then source 0x1900000; fi; fi; run $modeboot"
 CONFIG_USE_PREBOOT=y
 CONFIG_CLOCKS=y
+CONFIG_SPL_MAX_SIZE=0x30000
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x20000