DMAEngine: Define interleaved transfer request api

Define a new api that could be used for doing fancy data transfers
like interleaved to contiguous copy and vice-versa.
Traditional SG_list based transfers tend to be very inefficient in
such cases as where the interleave and chunk are only a few bytes,
which call for a very condensed api to convey pattern of the transfer.
This api supports all 4 variants of scatter-gather and contiguous transfer.

Of course, neither can this api help transfers that don't lend to DMA by
nature, i.e, scattered tiny read/writes with no periodic pattern.

Also since now we support SLAVE channels that might not provide
device_prep_slave_sg callback but device_prep_interleaved_dma,
remove the BUG_ON check.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Acked-by: Barry Song <Baohua.Song@csr.com>
[renamed dmaxfer_template to dma_interleaved_template
 did fixup after the enum dma_transfer_merge]
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

Documentation/dmaengine.txt

@@ -75,6 +75,10 @@ The slave DMA usage consists of following steps:
    slave_sg	- DMA a list of scatter gather buffers from/to a peripheral
    dma_cyclic	- Perform a cyclic DMA operation from/to a peripheral till the
 		  operation is explicitly stopped.
+   interleaved_dma - This is common to Slave as well as M2M clients. For slave
+		 address of devices' fifo could be already known to the driver.
+		 Various types of operations could be expressed by setting
+		 appropriate values to the 'dma_interleaved_template' members.
 
    A non-NULL return of this transfer API represents a "descriptor" for
    the given transaction.
@@ -89,6 +93,10 @@ The slave DMA usage consists of following steps:
 		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
 		size_t period_len, enum dma_data_direction direction);
 
+	struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)(
+		struct dma_chan *chan, struct dma_interleaved_template *xt,
+		unsigned long flags);
+
    The peripheral driver is expected to have mapped the scatterlist for
    the DMA operation prior to calling device_prep_slave_sg, and must
    keep the scatterlist mapped until the DMA operation has completed.