davinci: da850evm/omapl138-lcdk: Move BSS to SDRAM because SRAM is full

davinci: da850evm/omapl138-lcdk: Move BSS to SDRAM because SRAM is full

In order to fully support SPL_OF_CONTROL, we need BSS to be a bit
larger. This patch relocates BSS to SDRAM instead of SRAM which
is similar to how ARMv7 boards (like OMAP2+) do it.

This means two new variables are required:
CONFIG_SPL_BSS_START_ADDR  set to DAVINCI_DDR_EMIF_DATA_BASE
CONFIG_SPL_BSS_MAX_SIZE is set to 0x1080000 which is 1 byte
before the location where U-Boot will load.

Signed-off-by: Adam Ford <aford173@gmail.com>