staging: axis-fifo: avoid parsing ignored device tree properties

[ Upstream commit ed6daf2b2832d9b07582a6ff884039afa9063206 ]

Some properties were parsed from the device tree and then ignored by the
driver. Some would return an error if absent from the device tree, then
return an error if they were found because they are unsupported by the
driver.

Avoid parsing unused properties and clearly explain in the documentation
the ignored / unsupported properties.

Signed-off-by: Quentin Deslandes <quentin.deslandes@itdev.co.uk>
Link: https://lore.kernel.org/r/20191101214232.16960-2-quentin.deslandes@itdev.co.uk


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 2ca34b508774 ("staging: axis-fifo: Correct handling of tx_fifo_depth for size validation")
Signed-off-by: Sasha Levin <sashal@kernel.org>