include: mspi: fold MSPI devicetree macros doc under MSPI group

Move MSPI devicetree macros documentation under MSPI group to not
clutter top-level device drivers page.

Signed-off-by: Benjamin Cabé <[email protected]>

Author: kartben

include/zephyr/drivers/mspi/devicetree.h

@@ -10,7 +10,7 @@
 /**
  * @brief MSPI Devicetree related macros
  * @defgroup mspi_devicetree MSPI Devicetree related macros
- * @ingroup io_interfaces
+ * @ingroup mspi_interface
  * @{
  */