misc: Kconfig: ensure adi-axi-data-offload.c compiled as module

As a bool, the driver cannot be compile as a module, even though the
driver supports it.

Signed-off-by: Jorge Marques <jorge.marques@analog.com>

Author: gastmaier

drivers/misc/Kconfig

@@ -51,7 +51,7 @@ config AD525X_DPOT_SPI
 	  module will be called ad525x_dpot-spi.
 
 config ADI_AXI_DATA_OFFLOAD
-	bool "support Analog Devices Data Offload Engine"
+	tristate "support Analog Devices Data Offload Engine"
 	depends on HAS_IOMEM
 	depends on OF
 	help