linux-wandboard

MLK-14765: Fix DCP SHA null hashes and output length

On imx6sl and imx6ull DCP writes at least 32 bytes in the output
buffer instead of hash length as documented. Add intermediate buffer
to prevent write out of bounds.

When requested to produce null hashes DCP fails to produce valid
output. Add software workaround to bypass hardware and return valid output.

Signed-off-by: Radu Solea <radu.solea@nxp.com>