net: 9p: fix refcount leak in p9_read_work() error handling

net: 9p: fix refcount leak in p9_read_work() error handling

[ Upstream commit 87a26539b580c4377f982733d21c51dce99e4c11 ]

p9_req_put need to be called when m->rreq->rc.sdata is NULL to avoid
temporary refcount leak.

Link: https://lkml.kernel.org/r/20220712104438.30800-1-hbh25y@gmail.com
Fixes: 10f61be1685d ("9p: Add refcount to p9_req_t")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
[Dominique: commit wording adjustments, p9_req_put argument fixes for rebase]
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>