smb: mark the new channel addition log as informational log with cifs_info

For multichannel mounts, when a new channel is successfully opened
we currently log 'successfully opened new channel on iface: <>' as
cifs_dbg(VFS..)  which is eventually translated into a pr_err log.
Marking these informational logs as error logs may lead to confusion
for users so they will now be logged as info logs instead.

Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>