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/am64x_evm_a53_defconfig b/configs/am64x_evm_a53_defconfig
index ed603a1..9e251c1 100644
--- a/configs/am64x_evm_a53_defconfig
+++ b/configs/am64x_evm_a53_defconfig
@@ -30,6 +30,7 @@
 CONFIG_SPL_LOAD_FIT_ADDRESS=0x81000000
 CONFIG_BOOTCOMMAND="run findfdt; run envboot; run init_${boot}; run get_kern_${boot}; run get_fdt_${boot}; run run_kern"
 CONFIG_BOARD_LATE_INIT=y
+CONFIG_SPL_MAX_SIZE=0x180000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SPL_STACK_R=y