Documentation: ACPI: move dsdt-override.txt to admin-guide/acpi and convert to reST

This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.

No essential content change.
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/acpi/dsdt-override.txt → Documentation/admin-guide/acpi/dsdt-override.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Overriding DSDT
+===============
+
 Linux supports a method of overriding the BIOS DSDT:
 
-CONFIG_ACPI_CUSTOM_DSDT builds the image into the kernel.
+CONFIG_ACPI_CUSTOM_DSDT - builds the image into the kernel.
 
 When to use this method is described in detail on the
 Linux/ACPI home page:

Documentation/admin-guide/acpi/index.rst

@@ -9,3 +9,4 @@ the Linux ACPI support.
    :maxdepth: 1
 
    initrd_table_override
+   dsdt-override