IB/mthca: Fix error return code in __mthca_init_one()

[ Upstream commit 39f24956 ]

Fix to return a negative error code from the mthca_cmd_init() error
handling case instead of 0, as done elsewhere in this function.

Fixes: 80fd8238 ("[PATCH] IB/mthca: Encapsulate command interface init")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Change-Id: I1b062d8bd0261bcdf116aaef13bcbe5edf88d7c5