drivers: video: add VIDEO_PIX_FMT_Y4

Add the format to video.h
```
/**
 * @code{.unparsed}
 *   0                   1                   2                   3
 * | 0000yyyy 0000Yyyy | 0000yyyy 0000Yyyy | 0000yyyy 0000Yyyy | ...
 * @Endcode
 */
```

Signed-off-by: Kurt Eckhardt <kurte@rockisland.com>

Author: KurtE

include/zephyr/drivers/video.h

@@ -1377,6 +1377,15 @@ int video_transfer_buffer(const struct device *src, const struct device *sink,
  */
 #define VIDEO_PIX_FMT_GREY VIDEO_FOURCC('G', 'R', 'E', 'Y')
 
+
+/**
+ * @code{.unparsed}
+ *   0                   1                   2                   3
+ * | 0000yyyy 0000Yyyy | 0000yyyy 0000Yyyy | 0000yyyy 0000Yyyy | 0000yyyy 0000Yyyy | ...
+ * @endcode
+ */
+#define VIDEO_PIX_FMT_Y4 VIDEO_FOURCC('Y', '0', '4', ' ')
+
 /**
  * @code{.unparsed}
  *   0          1          2          3          3 2 1 0
@@ -1892,6 +1901,7 @@ static inline unsigned int video_bits_per_pixel(uint32_t pixfmt)
 	case VIDEO_PIX_FMT_Y16:
 	case VIDEO_PIX_FMT_NV16:
 	case VIDEO_PIX_FMT_NV61:
+	case VIDEO_PIX_FMT_Y4:
 		return 16;
 	case VIDEO_PIX_FMT_BGR24:
 	case VIDEO_PIX_FMT_RGB24: