virtiofs fix leak in setup

virtiofs fix leak in setup

[ Upstream commit 66ab33bf6d4341574f88b511e856a73f6f2a921e ]

This can be triggered for example by adding the "-omand" mount option,
which will be rejected and virtio_fs_fill_super() will return an error.

In such a case the allocations for fuse_conn and fuse_mount will leak due
to s_root not yet being set and so ->put_super() not being called.

Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>