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/orangepi_zero2_defconfig b/configs/orangepi_zero2_defconfig
index 4788102..d9c89c8 100644
--- a/configs/orangepi_zero2_defconfig
+++ b/configs/orangepi_zero2_defconfig
@@ -10,6 +10,7 @@
 CONFIG_MMC0_CD_PIN="PF6"
 CONFIG_R_I2C_ENABLE=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SPL_MAX_SIZE=0xbfa0
 CONFIG_SPL_I2C=y
 CONFIG_SYS_PBSIZE=1024
 CONFIG_SPL_SYS_I2C_LEGACY=y