configs: disable SPL_BOOTZ to preserve spl size

configs: disable SPL_BOOTZ to preserve spl size

In the existing behaviour, CMD_BOOTZ is not enabled by default which
means zimage.o is not compiled in the SPL in falcon mode unless
explicitly enabled. This changes now as SPL_BOOTZ is default y for
falcon users which leads to larger SPL size with zimage.o being present.

This patch modifies the defconfigs that used falcon mode but don't
require zimage support.

Signed-off-by: Anshul Dalal <anshuld@ti.com>