ti_armv7_common.h: Adjust malloc pool size in all cases.

ti_armv7_common.h: Adjust malloc pool size in all cases.

Previously we had been adjusting CONFIG_SYS_MALLOC_LEN based on if
CONFIG_DFU_MMC has been set or not.  However, for quite some time this
has not been the case as we often include <configs/ti_armv7_common.h>
prior to setting CONFIG_DFU_MMC so we would always use 16MiB and then
not have enough room for to DFU files.  Given the amount of memory we
always have, setting a minimum size of 32MiB for malloc is reasonable.
However, in the SPL case not only do we not need that much we start
running into overlap problems and then will fail to boot.  Since we
don't need 16MiB in the SPL case, bring this down to 8MiB.

Signed-off-by: Tom Rini <trini@konsulko.com>