net: mscc: ocelot: add missing lock protection in ocelot_port_xmit_inj()

In the Linux kernel, the following vulnerability has been resolved: net: mscc: ocelot: add missing lock protection in ocelot_port_xmit_inj() ocelot_port_xmit_inj() calls ocelot_can_inject() and ocelot_port_inject_frame() without holding the injection group lock. Both functions contain lockdep_assert_held() for the injection lock, and the correct caller felix_port_deferred_xmit() properly acquires the lock using ocelot_lock_inj_grp() before calling these functions. Add ocelot_lock_inj_grp()/ocelot_unlock_inj_grp() around the register injection path to fix the missing lock protection. The FDMA path is not affected as it uses its own locking mechanism.