This compatible adds the ability for dw spi controller driver to work with
the dw spi controller found on Alpine chips.

The dw spi controller has an auto-deselect of Chip-Select, in case there is
no data inside the Tx FIFO. While working on platforms with Alpine chips,
auto-deselect mode causes an issue for some spi devices that can't handle
the Chip-Select deselect in the middle of a transaction. It is a normal
behavior for a Tx FIFO to be empty in the middle of a transaction, due to
busy cpu. In the Alpine chip family an option to change the default
behavior was added to the original dw spi controller to prevent this issue
of de-asserting Chip-Select once TX FIFO is empty. The change was to allow
SW manual control of the Chip-Select. With this change, as long as the
Slave Enable Register is asserted, the Chip-Select will be asserted. As a
result, it is necessary to deselect the Slave Select Register once the
transaction is done. This feature is enabled via a new device compatible
string called 'amazon,alpine-dw-apb-ssi'.  Once the driver identifies the
new compatible string, it enables the hw fixup logic, by writing to a
dedicated register found in the IP reserved area and will start manual
deselecting the Slave Select Register when the transfer ends.
Signed-off-by: Talel Shenhar <talel@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>