ASoC: Intel: Skylake: Use struct_size() helper

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 the following form:

uuid_params->num_modules * sizeof(struct skl_mod_inst_map) + sizeof(uuid_params->num_modules)

with:

struct_size(params, u.map, uuid_params->num_modules)

and so on...

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>