net: sched: em_text: fix possible memory leak in em_text_destroy()

m->data needs to be freed when em_text_destroy is called.

Fixes: d675c989 ("[PKT_SCHED]: Packet classification based on textsearch (ematch)")
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>