docs: firmware-guide: ACPI: Replace dma_request_slave_channel() with dma_request_chan()

dma_request_chan() is the preferred API to request slave channels.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
[ rjw: Subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/firmware-guide/acpi/enumeration.rst

@@ -71,8 +71,8 @@ DMA support
 DMA controllers enumerated via ACPI should be registered in the system to
 provide generic access to their resources. For example, a driver that would
 like to be accessible to slave devices via generic API call
-dma_request_slave_channel() must register itself at the end of the probe
-function like this::
+dma_request_chan() must register itself at the end of the probe function like
+this::
 
 	err = devm_acpi_dma_controller_register(dev, xlate_func, dw);
 	/* Handle the error if it's not a case of !CONFIG_ACPI */
@@ -112,15 +112,15 @@ could look like::
 	}
 	#endif
 
-dma_request_slave_channel() will call xlate_func() for each registered DMA
-controller. In the xlate function the proper channel must be chosen based on
+dma_request_chan() will call xlate_func() for each registered DMA controller.
+In the xlate function the proper channel must be chosen based on
 information in struct acpi_dma_spec and the properties of the controller
 provided by struct acpi_dma.
 
-Clients must call dma_request_slave_channel() with the string parameter that
-corresponds to a specific FixedDMA resource. By default "tx" means the first
-entry of the FixedDMA resource array, "rx" means the second entry. The table
-below shows a layout::
+Clients must call dma_request_chan() with the string parameter that corresponds
+to a specific FixedDMA resource. By default "tx" means the first entry of the
+FixedDMA resource array, "rx" means the second entry. The table below shows a
+layout::
 
 	Device (I2C0)
 	{