spi: spi-gpio: Use 'cansleep' variants to access GPIO

The GPIO chip in use could be of any kind, and therefore might sleep
when accesing the GPIO lines. Take account of this by using cansleep
instead, which is the most generic case.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Mark Brown <broonie@linaro.org>