ath10k: coredump: use struct_size() helper

ath10k: coredump: 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 code of the following form:

sizeof(*ce_hdr) + CE_COUNT * sizeof(ce_hdr->entries[0])

with:

struct_size(ce_hdr, entries, CE_COUNT)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>