staging: rtl8723bs: fix missing transmission lock in rtw_xmit

staging: rtl8723bs: fix missing transmission lock in rtw_xmit

The packet transmission path in rtw_xmit.c contained TODO comments
indicating a missing lock. This patch implements spin_lock_bh and
spin_unlock_bh around the station attribute update section.

This prevents a potential race condition where station security and
PHY information could be modified on another CPU core during
transmission. The use of _bh variants ensures safety in bottom-half
contexts common in network transmit paths.

Verified that psta is NULL-checked prior to acquisition and that no
double-unlocks occur on the exit path.

Signed-off-by: Karthikey D Kadati <karthikey3608@gmail.com>
Link: https://patch.msgid.link/20251227113348.26272-1-karthikey3608@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>