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/db-88f6820-amc_defconfig b/configs/db-88f6820-amc_defconfig
index dcf1ffd..248be49 100644
--- a/configs/db-88f6820-amc_defconfig
+++ b/configs/db-88f6820-amc_defconfig
@@ -25,6 +25,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_SPL_MAX_SIZE=0x22fd0
+CONFIG_SPL_BSS_MAX_SIZE=0x4000
 CONFIG_SPL_I2C=y
 CONFIG_SYS_MAXARGS=96
 # CONFIG_CMD_FLASH is not set