ASoC: SOF: Add some bounds checking to firmware data

Smatch complains about "head->full_size - head->header_size" can
underflow.  To some extent, we're always going to have to trust the
firmware a bit.  However, it's easy enough to add a check for negatives,
and let's add a upper bounds check as well.

Fixes: d2458baa ("ASoC: SOF: ipc3-loader: Implement firmware parsing and loading")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://msgid.link/r/5593d147-058c-4de3-a6f5-540ecb96f6f8@moroto.mountain


Signed-off-by: Mark Brown <broonie@kernel.org>