Driver improvements (#535)

- New drivers:
  - SD SPI
  - spi_peripheral
  - touch_placeholder
  - display_placeholder
- Devicetree compiler:
  - Implement phandle-arrays
  - Implement device addresses
- Add placeholder drivers to all devices with a SPI display
- SPI driver: add `cs-pins` and set them to high on driver start
- FileSystem: add `file_system_set_owner()` and `file_system_get_owner()`
- File locking is now checking if the related `FileSystem` is part of a shared SPI bus
- Add `device_get_child_count()`
- SDMMC driver: Remove default of `slot` value
- Fix for Crowpanel Basic 3.5" display (add delay to booting)
- Fix for LilyGO T-HMI SD card mounting (delayed mounting by disabling it initially in the dts)

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

@@ -0,0 +1,23 @@
+description: ESP32 SD card over SPI
+
+compatible: "espressif,esp32-sdspi"
+
+bus: spi
+
+properties:
+  pin-cd:
+    type: phandles
+    default: GPIO_PIN_SPEC_NONE
+    description: Card detect GPIO
+  pin-wp:
+    type: phandles
+    default: GPIO_PIN_SPEC_NONE
+    description: Write protect GPIO
+  pin-int:
+    type: phandles
+    default: GPIO_PIN_SPEC_NONE
+    description: Interrupt GPIO
+  frequency-khz:
+    type: int
+    required: true
+    description: SPI clock frequency in kHz