docs: firmware-guide: acpi: avoid using ReST :doc:`foo` markup

The :doc:`foo` tag is auto-generated via automarkup.py.
So, use the filename at the sources, instead of :doc:`foo`.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Link: https://lore.kernel.org/r/7162043c18f1ea96c446b332400e44e8087ba142.1623824363.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/firmware-guide/acpi/dsd/data-node-references.rst

@@ -79,7 +79,8 @@ the ANOD object which is also the final target node of the reference.
 	    })
 	}
 
-Please also see a graph example in :doc:`graph`.
+Please also see a graph example in
+Documentation/firmware-guide/acpi/dsd/graph.rst.
 
 References
 ==========

Documentation/firmware-guide/acpi/dsd/graph.rst

@@ -174,4 +174,4 @@ References
     referenced 2016-10-04.
 
 [7] _DSD Device Properties Usage Rules.
-    :doc:`../DSD-properties-rules`
+    Documentation/firmware-guide/acpi/DSD-properties-rules.rst

Documentation/firmware-guide/acpi/enumeration.rst

@@ -339,8 +339,8 @@ a code like this::
 There are also devm_* versions of these functions which release the
 descriptors once the device is released.
 
-See Documentation/firmware-guide/acpi/gpio-properties.rst for more information about the
-_DSD binding related to GPIOs.
+See Documentation/firmware-guide/acpi/gpio-properties.rst for more information
+about the _DSD binding related to GPIOs.
 
 MFD devices
 ===========
@@ -460,7 +460,8 @@ the _DSD of the device object itself or the _DSD of its ancestor in the
 Otherwise, the _DSD itself is regarded as invalid and therefore the "compatible"
 property returned by it is meaningless.
 
-Refer to :doc:`DSD-properties-rules` for more information.
+Refer to Documentation/firmware-guide/acpi/DSD-properties-rules.rst for more
+information.
 
 PCI hierarchy representation
 ============================