mxs/dma: Enlarge the CCW descriptor area to 4 pages

mxs/dma: Enlarge the CCW descriptor area to 4 pages

In case of a large SPI flash, the amount of DMA descriptors
available to the DMA driver is not large enough anymore. For
example 8MB SPI flash now needs 129 descriptors to be transfered
in one long read. There are currently 53 descriptors available in
one PAGE_SIZE-big block. Enlarge the allocated descriptor area to
four PAGE_SIZE blocks to fulfill such requirements.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Dan Williams <djbw@fb.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>