wifi: mac80211: Write cnt before copying in ieee80211_copy_rnr_beacon()

wifi: mac80211: Write cnt before copying in ieee80211_copy_rnr_beacon()

While I caught the need for setting cnt early in nl80211_parse_rnr_elems()
in the original annotation of struct cfg80211_rnr_elems with __counted_by,
I missed a similar pattern in ieee80211_copy_rnr_beacon(). Fix this by
moving the cnt assignment to before the loop.

Fixes: 7b6d7087031b ("wifi: cfg80211: Annotate struct cfg80211_rnr_elems with __counted_by")
Signed-off-by: Kees Cook <kees@kernel.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://patch.msgid.link/20250721182521.work.540-kees@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>