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/j7200_evm_r5_defconfig b/configs/j7200_evm_r5_defconfig
index 4883e8a..451f25c 100644
--- a/configs/j7200_evm_r5_defconfig
+++ b/configs/j7200_evm_r5_defconfig
@@ -28,6 +28,7 @@
 # CONFIG_USE_SPL_FIT_GENERATOR is not set
 CONFIG_USE_BOOTCOMMAND=y
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SPL_MAX_SIZE=0xc0000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_SEPARATE_BSS=y