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/roc-cc-rk3308_defconfig b/configs/roc-cc-rk3308_defconfig
index 0ae45ca..f90c363 100644
--- a/configs/roc-cc-rk3308_defconfig
+++ b/configs/roc-cc-rk3308_defconfig
@@ -22,6 +22,8 @@
 CONFIG_BOOTDELAY=0
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SPL_MAX_SIZE=0x20000
+CONFIG_SPL_PAD_TO=0x7f8000
 CONFIG_SPL_STACK_R=y
 # CONFIG_CMD_BDI is not set
 # CONFIG_CMD_CONSOLE is not set