ASoC: qdsp6: q6core: Use struct_size() in kmemdup()

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes, in particular in the
context in which this code is being used.

So, replace code of the following form:

sizeof(*fwk) + fwk->num_services * sizeof(fwk->svc_api_info[0]);

with:

struct_size(fwk, svc_api_info, fwk->num_services)

and so on...

Notice that variables bytes and len are unnecessary, hence they are
removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>