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/imx7_cm_defconfig b/configs/imx7_cm_defconfig
index e6b1466..912b3a6 100644
--- a/configs/imx7_cm_defconfig
+++ b/configs/imx7_cm_defconfig
@@ -24,6 +24,7 @@
 CONFIG_BOOTCOMMAND="run boot${boot-mode}"
 CONFIG_DEFAULT_FDT_FILE="ask"
 # CONFIG_BOARD_EARLY_INIT_F is not set
+CONFIG_SPL_MAX_SIZE=0xe000
 CONFIG_SPL_I2C=y
 CONFIG_SPL_USB_HOST=y
 CONFIG_SPL_USB_GADGET=y