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/topic_miamiplus_defconfig b/configs/topic_miamiplus_defconfig
index bd70cb7..a402478 100644
--- a/configs/topic_miamiplus_defconfig
+++ b/configs/topic_miamiplus_defconfig
@@ -26,6 +26,7 @@
 CONFIG_USE_PREBOOT=y
 CONFIG_CLOCKS=y
 CONFIG_SPL_MAX_SIZE=0x30000
+CONFIG_SPL_BSS_MAX_SIZE=0x100000
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x20000