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/am65x_evm_r5_usbmsc_defconfig b/configs/am65x_evm_r5_usbmsc_defconfig
index 3d8b6de..41fabd4 100644
--- a/configs/am65x_evm_r5_usbmsc_defconfig
+++ b/configs/am65x_evm_r5_usbmsc_defconfig
@@ -22,6 +22,7 @@
 CONFIG_SPL_LOAD_FIT=y
 CONFIG_USE_BOOTCOMMAND=y
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SPL_MAX_SIZE=0x58000
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_SEPARATE_BSS=y
 CONFIG_SPL_EARLY_BSS=y