spi: xilinx_spi: Add support ops to axi qspi driver

spi: xilinx_spi: Add support ops to axi qspi driver

Add support_ops function to check controller supported operations by
spi-mem framework. Current default support ops function does not allow
dummy buswidth no more than 1, unless we are using buswidth is 4 for TX.
In order to support dummy buswidth > 1 by spi-nor framework we are adding
explicit support_ops to check controller supported operations.

Fix dummy bytes calculation incase of valid dummy bytes when dummy
buswidth is > 1. Current dummy bytes calculation does not provide
correct dummy values for dummy buswidth > 1.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Link: https://lore.kernel.org/r/1657954727-31972-3-git-send-email-ashok.reddy.soma@xilinx.com
Signed-off-by: Michal Simek <michal.simek@amd.com>