octeontx2-vf: Fix error return code in otx2vf_probe()

Fix to return negative error code -ENOMEM from the alloc failed error
handling case instead of 0, as done elsewhere in this function.

Fixes: 3184fb5b

 ("octeontx2-vf: Virtual function driver support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>