wifi: mac80211: make rate u32 in sta_set_rate_info_rx()

The value of last_rate in ieee80211_sta_rx_stats is degraded from u32 to
u16 after being assigned to rate variable, which causes information loss
in STA_STATS_FIELD_TYPE and later bitfields.

Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Link: https://lore.kernel.org/r/20230209110659.25447-1-shayne.chen@mediatek.com
Fixes: 41cbb0f5

 ("mac80211: add support for HE")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>