serial: atmel_sam3: remove driver as it was deprecated

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

dts/bindings/serial/atmel,sam3x-uart.yaml

@@ -1,30 +0,0 @@
----
-title: SAM3X UART
-id: atmel,sam3x-uart
-version: 0.1
-
-description: >
-    This binding gives a base representation of the SAM3X UART
-
-inherits:
-  - !include uart.yaml
-
-properties:
-  - compatible:
-      type: string
-      category: required
-      description: compatible strings
-      constraint: "atmel,sam3x-uart"
-
-  - reg:
-      type: array
-      description: mmio register space
-      generation: define
-      category: required
-
-  - interrupts:
-      type: array
-      category: required
-      description: required interrupts
-      generation: define
-...