greybus: spi: move chipselect to one byte size

Fixed in the specification, some values for chipselect count and index
were different in size, just fix that for all reference to chipselect
and move all to one byte size and remove byte order operations.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>