dma: xilinx: Get DMA alignment from device tree for Framebuffer

dma: xilinx: Get DMA alignment from device tree for Framebuffer

Patch adds xlnx,pixels-per-clock(ppc) and xlnx,dma-align device tree
property decoding to calculate the required DMA alignment.
xlnx,pixels-per-clock is mandatory property now.
Minimum alignment required is 8 * pixels per clock in bytes.
dma-align property is optional.

In case present, dma-align must be a power of 2 and be >= 8 * ppc.
If absent, alignment is set as ppc * 8.

Added a new compatible string and structure which contains dma direction
and flag. The flag would be a bitmask of properties.
When ever a new IP or device tree property is to be supported, a bitmask
for the same is to be created and added to this flag.

For the new v2.1 compatible string, a new XILINX_PPC_PROP bitmask is
set in the flags. If the flag is set then, pixels-per-clock property
would be checked.

Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
Reviewed-by: Radhey Shyam Pandey <radheys@xilinx.com>
Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>