Patch: Make ACPI subsystem provide CEDT table

[Robert Kiraly <me@boldcoder.com>]

This is a simple ACPI patch. I'm submitting a revised version to 
linux-acpi per Rafael Wysocki and linux-cxl per Dan Williams.

The patch has been moved to the message body and a Signed-off-by tag has 
been added. Thunderbird has added CRs so "patch -p1 -l" is needed. To 
address other points:

Q. Dan Williams said: Yes, although I don't see much incremental benefit 
to developers publishing a root only raw table... So, not opposed to the 
patch, but I want to direct you to the sysfs representation of the CEDT 
and CFMWS in /sys/bus/cxl/devices... Platform firmware CXL details are 
modeled as "CXL root" objects in the /sys/bus/cxl device model.

A. The patch is being submitted in connection with work on a CXL bridge. 
The developers would like to express appreciation for the "sysfs" point. 
They find it useful to be able to do initialization through the table 
but will look at the "sysfs" approach.

Q. Rafael J. Wysocki said: I'm not sure why the #ifdef is needed.

A. I reviewed cxl-next and decided to add the #ifdef to ensure that the 
code would compile regardless of the direction that the codebase takes.

==== start of patch ====
Subject: Make ACPI subsystem provide CEDT table
Signed-off-by: Robert Kiraly <me@boldcoder.com>

This is a simple patch to the ACPI subsystem. The patch adds ACPI
_SIG_CEDT to table_sigs[] in  "drivers/acpi/tables.c".

Presently,  CXL code isn't able to make use of the  CEDT table at
the initrd stage. Subsequent to the change, the CEDT table can be
used.

If  a developer  plans to use the CEDT table to  program  the CXL
ports,  this change is needed.  Otherwise,  it isn't  expected to
make a difference.

I certify  compliance with  Developer’s Certificate of Origin 1.1
as listed in:
https://www.kernel.org/doc/html/v4.10/process/submitting-patches.
html

--- linux-5.16.old/drivers/acpi/tables.c
+++ linux-5.16/drivers/acpi/tables.c
@@ -500,6 +500,9 @@
  	ACPI_SIG_WDDT, ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT,
  	ACPI_SIG_PSDT, ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT,
  	ACPI_SIG_IORT, ACPI_SIG_NFIT, ACPI_SIG_HMAT, ACPI_SIG_PPTT,
+#ifdef ACPI_SIG_CEDT
+       ACPI_SIG_CEDT,
+#endif
  	ACPI_SIG_NHLT };

  #define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)
==== end of patch ====