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/T1024RDB_NAND_defconfig b/configs/T1024RDB_NAND_defconfig
index 2189856..f328cfd 100644
--- a/configs/T1024RDB_NAND_defconfig
+++ b/configs/T1024RDB_NAND_defconfig
@@ -32,6 +32,8 @@
 CONFIG_BOARD_EARLY_INIT_R=y
 CONFIG_ID_EEPROM=y
 # CONFIG_SPL_FRAMEWORK is not set
+CONFIG_SPL_MAX_SIZE=0x28000
+CONFIG_SPL_PAD_TO=0x40000
 CONFIG_SPL_NAND_BOOT=y
 CONFIG_SPL_FSL_PBL=y
 CONFIG_SPL_FLUSH_IMAGE=y