A multi link bankswitch can be done if the hardware supports and
the stream is handled by multiple Master(s).

This preparatory patch adds support to track m_rt in a stream.
Modifying m_rt_count and usage is added as part of the next patch.
Signed-off-by: NShreyas NC <shreyas.nc@intel.com>
Acked-by: NPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVinod Koul <vkoul@kernel.org>