Adds functions to link and unlink source channels to sink
channels in the FSU:
int ipu_fsu_link(struct ipu_soc *ipu, int src_ch, int sink_ch);
int ipu_fsu_unlink(struct ipu_soc *ipu, int src_ch, int sink_ch);
The channels numbers are usually IDMAC channels, but they can also be
channels that do not transfer data to or from memory. The following
convenience functions can be used in place of ipu_fsu_link/unlink()
when both source and sink channels are IDMAC channels:
int ipu_idmac_link(struct ipuv3_channel *src, struct ipuv3_channel *sink);
int ipu_idmac_unlink(struct ipuv3_channel *src, struct ipuv3_channel *sink);