spi/gpio: Fix stub for spi_gpio_probe_dt()

The gpio_ was missing from the name.  Add a name for the parameter while
we're at it since GCC warns.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index aed1615..a2b50c5 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -386,7 +386,7 @@
 	return ret;
 }
 #else
-static inline int spi_probe_dt(struct platform_device *)
+static inline int spi_gpio_probe_dt(struct platform_device *pdev)
 {
 	return 0;
 }