tests: drivers: sensor: spi: include gpio.h header

This patch adds a missing include directive to `spi.dtsi` in the
`build_all` configuration.The include is required because commit
2ac3164 introduced the use of `GPIO_ACTIVE_HIGH` and `GPIO_ACTIVE_LOW`
macros.

Signed-off-by: Patryk Koscik <pkoscik@antmicro.com>

Author: pkoscik

tests/drivers/build_all/sensor/spi.dtsi

@@ -6,6 +6,8 @@
  * Application overlay for spi devices
  */
 
+#include <zephyr/dt-bindings/gpio/gpio.h>
+
 /****************************************
  * PLEASE KEEP REG ADDRESSES SEQUENTIAL *
  ***************************************/