spi: dw: Add 32 bpw support to SPI DW DMA driver

Add Support for AxSize = 4 bytes configuration from dw dma driver if
n_bytes i.e. number of bytes per write to fifo is 4.

Number of bytes written to fifo per write is depended on the bits/word
configuration being used which the DW core driver translates to n_bytes.
Hence, for bits per word values between 17 and 32 n_bytes should be
equal to 4.

* tested on Baikal-T1 based system with DW SPI-looped back interface
transferring a chunk of data with DFS:8,12,16.

Signed-off-by: Joy Chakraborty <joychakr@google.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20230427123314.1997152-2-joychakr@google.com


Signed-off-by: Mark Brown <broonie@kernel.org>