thermal: int340x: Use struct_group() for memcpy() region

In preparation for FORTIFY_SOURCE performing compile-time and
run-time field bounds checking for memcpy(), avoid intentionally
writing across neighboring fields.

Use struct_group() in struct art around members weight, and
ac[0-9]_max, so they can be referenced together. This will allow
memcpy() and sizeof() to more easily reason about sizes, improve
readability, and avoid future warnings about writing beyond the
end of weight.

"pahole" shows no size nor member offset changes to struct art.
"objdump -d" shows no meaningful object code changes (i.e. only
source line number induced differences).

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>