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/socfpga_de10_nano_defconfig b/configs/socfpga_de10_nano_defconfig
index 7a02299..9ae804f 100644
--- a/configs/socfpga_de10_nano_defconfig
+++ b/configs/socfpga_de10_nano_defconfig
@@ -18,6 +18,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_CLOCKS=y
+CONFIG_SPL_PAD_TO=0x10000
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x40000
 CONFIG_SYS_MAXARGS=32