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/omapl138_lcdk_defconfig b/configs/omapl138_lcdk_defconfig
index 799dc40..0ae02d9 100644
--- a/configs/omapl138_lcdk_defconfig
+++ b/configs/omapl138_lcdk_defconfig
@@ -31,6 +31,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_CLOCKS=y
 CONFIG_MISC_INIT_R=y
+CONFIG_SPL_PAD_TO=0x8000
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0xb5
 CONFIG_SPL_NAND_SUPPORT=y