qed: Fix PTT leak in qed_drain()

[ Upstream commit 9aaa4e8ba12972d674caeefbc5f88d83235dd697 ]

Release PTT before entering error flow.

Signed-off-by: Denis Bolotin <denis.bolotin@cavium.com>
Signed-off-by: Michal Kalderon <michal.kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>