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_n5x_defconfig b/configs/socfpga_n5x_defconfig
index 1fd4131..3a17ace 100644
--- a/configs/socfpga_n5x_defconfig
+++ b/configs/socfpga_n5x_defconfig
@@ -19,6 +19,7 @@
 CONFIG_BOOTARGS="earlycon panic=-1 earlyprintk=ttyS0,115200"
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run fatscript; run mmcload; run linux_qspi_enable; run mmcboot"
+CONFIG_SPL_MAX_SIZE=0x40000
 CONFIG_SPL_CACHE=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x3c00000