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/sama5d2_xplained_spiflash_defconfig b/configs/sama5d2_xplained_spiflash_defconfig
index e494893..4364e41 100644
--- a/configs/sama5d2_xplained_spiflash_defconfig
+++ b/configs/sama5d2_xplained_spiflash_defconfig
@@ -36,6 +36,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_MISC_INIT_R=y
 CONFIG_SPL_MAX_SIZE=0x10000
+CONFIG_SPL_BSS_MAX_SIZE=0x80000
 CONFIG_SPL_DM_SPI_FLASH=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x10000