docs: dt: unittest: Correct SELFTEST to UNITTEST

The Kconfig switch is CONFIG_OF_UNITTEST. Not OF_SELFTEST.
Correct this.

While at it replace the outdated file list with a link to the
directory as proposed by Rob Herring.

Cc: Gaurav Minocha <[e-mail]>
Cc: Rob Herring <[e-mail]>
Signed-off-by: Dirk Behme <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

Documentation/devicetree/of_unittest.rst

···
 
 The Device Tree Source file (drivers/of/unittest-data/testcases.dts) contains
 the test data required for executing the unit tests automated in
-drivers/of/unittest.c. Currently, following Device Tree Source Include files
-(.dtsi) are included in testcases.dts::
+drivers/of/unittest.c. See the content of the folder::
 
-    drivers/of/unittest-data/tests-interrupts.dtsi
-    drivers/of/unittest-data/tests-platform.dtsi
-    drivers/of/unittest-data/tests-phandle.dtsi
-    drivers/of/unittest-data/tests-match.dtsi
+    drivers/of/unittest-data/tests-*.dtsi
 
-When the kernel is build with OF_SELFTEST enabled, then the following make
+for the Device Tree Source Include files (.dtsi) included in testcases.dts.
+
+When the kernel is build with CONFIG_OF_UNITTEST enabled, then the following make
 rule::
 
     $(obj)/%.dtb: $(src)/%.dts FORCE

Documentation/translations/zh_CN/devicetree/of_unittest.rst

···
     drivers/of/unittest-data/tests-phandle.dtsi
     drivers/of/unittest-data/tests-match.dtsi
 
-当内核在启用OF_SELFTEST的情况下被构建时，那么下面的make规则::
+当内核在启用CONFIG_OF_UNITTEST的情况下被构建时，那么下面的make规则::
 
     $(obj)/%.dtb: $(src)/%.dts FORCE
 	    $(call if_changed_dep, dtc)