Add cs_gpios to esp32_spi driver

Platforms/platform-esp32/bindings/espressif,esp32-spi.yaml

@@ -34,5 +34,9 @@ properties:
     type: int
     default: 0
     description: |
-      Data transfer size limit in bytes. 
+      Data transfer size limit in bytes.
       0 means the platform decides the limit.
+  cs-gpios:
+    type: phandle-array
+    default: { 0 }
+    description: Null-terminated array of chip select GPIO pin specs for peripherals on this bus

Platforms/platform-esp32/include/tactility/drivers/esp32_spi.h

@@ -23,6 +23,8 @@ struct Esp32SpiConfig {
     struct GpioPinSpec pin_hd;
     /** Data transfer size limit in bytes. 0 means the platform decides the limit. */
     int max_transfer_size;
+    /** Null-terminated array of chip select GPIO pin specs */
+    struct GpioPinSpec cs_gpios[];
 };
 
 #ifdef __cplusplus