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/iot2050_defconfig b/configs/iot2050_defconfig
index 6cabc10..d307d75 100644
--- a/configs/iot2050_defconfig
+++ b/configs/iot2050_defconfig
@@ -32,6 +32,7 @@
 CONFIG_CONSOLE_MUX=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SPL_MAX_SIZE=0x58000
+CONFIG_SPL_BSS_MAX_SIZE=0x80000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SPL_STACK_R=y