mac80211: ath: add struct_group for struct ath_cycle_counters

mac80211: ath: add struct_group for struct ath_cycle_counters

Add a struct_group to around all members in struct ath_cycle_counters.
It can help the compiler detect the intended bounds of the memcpy() and
memset().

This patch fixes the following build warning:

In function 'fortify_memset_chk',
    inlined from 'ath9k_ps_wakeup' at /home/db/openwrt/build_dir/target-mips_24kc_musl/linux-ath79_generic/backports-6.1.24/drivers/net/wireless/ath/ath9k/main.c:140:3:
./include/linux/fortify-string.h:314:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
  314 |                         __write_overflow_field(p_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Shiji Yang <yangshiji66@qq.com>