Convert CONFIG_SPL_BSS_MAX_SIZE et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_BSS_MAX_SIZE
   CONFIG_SPL_MAX_FOOTPRINT

Note that the da850evm platforms were violating the "only use one" rule
here, and so now hard-code their BSS limit.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/kontron_sl28_defconfig b/configs/kontron_sl28_defconfig
index fcc6dd3..bf25292 100644
--- a/configs/kontron_sl28_defconfig
+++ b/configs/kontron_sl28_defconfig
@@ -36,6 +36,7 @@
 CONFIG_BOARD_LATE_INIT=y
 CONFIG_PCI_INIT_R=y
 CONFIG_SPL_MAX_SIZE=0x20000
+CONFIG_SPL_BSS_MAX_SIZE=0x100000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_SPL_SPI_LOAD=y