xen: Drop xenoprofile support

The most recent xenoprof change was 300ef0cb4f ("x86: Add Xenoprofile
support for AMD Family16h") in 2013, despite there being 42 changes worth of
other cleanup/rearranging since then.

Oprofile themselves dropped Xen support in commit 0c142c3a096d ("Remove
opcontrol and the GUI and processor models dependent on it") in 2014, as part
of releasing version 1.0 and switching over to using operf based on the Linux
perf_event subsystem.  Linux's version of this patch was merged in commit
24880bef417f ("Merge tag 'oprofile-removal-5.12'") in 2021.

Drop xenoprof and all supporting infrastructure, including the hypercall, the
XSM hook and flask vectors which lose their only caller, and even shrinks
struct domain by one pointer which wasn't properly excluded in
!CONFIG_XENOPROF builds.

Retain the public xenoprof.h header as it is ABI, but note that the
functionality is removed.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Teddy Astie <teddy.astie@vates.tech>
Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Daniel P. Smith <dpsmith@apertussolutions.com>

CHANGELOG.md

@@ -15,6 +15,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
    - The cpuid_mask_* command line options for legacy AMD CPUs.  These were
      deprecated in Xen 4.7 and noted not to work correctly with AMD CPUs from
      2011 onwards.
+   - Xenoprofile support.  Oprofile themselves removed support for Xen in 2014
+     prior to the version 1.0 release, and there has been no development since
+     before then in Xen.
 
 ## [4.21.0](https://xenbits.xenproject.org/gitweb/?p=xen.git;a=shortlog;h=RELEASE-4.21.0) - 2025-11-19