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/imx8mp_rsb3720a1_4G_defconfig b/configs/imx8mp_rsb3720a1_4G_defconfig
index e3e9bc7..6a03f67 100644
--- a/configs/imx8mp_rsb3720a1_4G_defconfig
+++ b/configs/imx8mp_rsb3720a1_4G_defconfig
@@ -34,6 +34,7 @@
 CONFIG_ARCH_MISC_INIT=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_BOARD_LATE_INIT=y
+CONFIG_SPL_MAX_SIZE=0x26000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_BOOTROM_SUPPORT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y