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/turris_omnia_defconfig b/configs/turris_omnia_defconfig
index b8b01e2..684d5d3 100644
--- a/configs/turris_omnia_defconfig
+++ b/configs/turris_omnia_defconfig
@@ -36,6 +36,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_MISC_INIT_R=y
+CONFIG_SPL_MAX_SIZE=0x22fd0
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y