rockchip: Restore support for boot scripts in legacy image format

rockchip: Restore support for boot scripts in legacy image format

Use of CONFIG_SPL_FIT_SIGNATURE=y cause CONFIG_LEGACY_IMAGE_FORMAT=n as
default, this prevent boot scripts in legacy image format from working
and was an unintended change in the listed fixes commits:

  Wrong image format for "source" command

Add CONFIG_LEGACY_IMAGE_FORMAT=y to defconfig for affected boards to
restore support for boot scripts in legacy image format.

Fixes: 3bf8e4080763 ("board: rockchip: add Radxa ROCK5B Rk3588 board")
Fixes: cf777572ca31 ("rockchip: rockpro64: Use SDMA to boost eMMC performance")
Fixes: 6e2b8344d60c ("rockchip: rock-pi-4: Use SDMA to boost eMMC performance")
Fixes: 1bf49d5a4a7c ("rockchip: rk3566-radxa-cm3-io: Update defconfig")
Fixes: 703c170b40f2 ("rockchip: rk3568-evb: Update defconfig")
Fixes: 68000f750acd ("rockchip: rk3568-rock-3a: Update defconfig")
Fixes: 6fb02589a608 ("rockchip: rk3588-evb: Update defconfig")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>