mac80211: replace DEFINE_SIMPLE_ATTRIBUTE with DEFINE_DEBUGFS_ATTRIBUTE

Fix the following coccicheck warning:
./drivers/net/wireless/mac80211_hwsim.c:1040:0-23: WARNING:
hwsim_fops_rx_rssi should be defined with
DEFINE_DEBUGFS_ATTRIBUTE

Signed-off-by: Yihao Han <hanyihao@vivo.com>
Link: https://lore.kernel.org/r/20220218070228.6210-1-hanyihao@vivo.com


[fix indentation]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>