rockchip: rk3308: Enable ARMv8 crypto and FIT checksum validation

rockchip: rk3308: Enable ARMv8 crypto and FIT checksum validation

The RK3308 SoC support ARMv8 Cryptography Extensions and use of the
ARMv8 crypto extensions help speed up FIT checksum validation in SPL.

Imply ARMV8_SET_SMPEN and ARMV8_CRYPTO to take advantage of the crypto
extensions for SHA256 when validating checksum of FIT images.

Imply SPL_FIT_SIGNATURE and LEGACY_IMAGE_FORMAT to enable FIT checksum
validation on all RK3308 boards.

Also disable CONFIG_SPL_RAW_IMAGE_SUPPORT in board defconfigs to ensure
SPL does not try to jump to code that failed checksum validation.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>