x86/shadow: Drop incorrect diagnostic when shadowing TSS.RSP0

x86/shadow: Drop incorrect diagnostic when shadowing TSS.RSP0

During development of the XTF pagewalk tests, I reliably encountered this
message exactly once per run.  It occurs when the first action to touch
TSS.RSP0 is an interrupt/exception taken in userspace, and the processor tries
to push the IRET frame.

Subsequently, OSSTest has demonstrated that it triggers frequently for a
KPTI-enabled kernel.

  (XEN) multi.c:3324:d1v1 write to pagetable during event injection: cr2=0xffffad2646687f38, mfn=0x2415a1
  [ 1411.949155] systemd-logind[2683]: New session 73 of user root.
  (XEN) multi.c:3324:d1v1 write to pagetable during event injection: cr2=0xffffad264671ff38, mfn=0x240a41
  (XEN) multi.c:3324:d1v1 write to pagetable during event injection: cr2=0xffffad2646837f38, mfn=0x2415c5
  (XEN) multi.c:3324:d1v1 write to pagetable during event injection: cr2=0xffffad26468a7f38, mfn=0x2414e7
  [ 1442.207473] systemd-logind[2683]: New session 74 of user root.
  [ 1471.452206] systemd-logind[2683]: New session 75 of user root.
  (XEN) multi.c:3324:d1v1 write to pagetable during event injection: cr2=0xffffad2646d17f08, mfn=0x2417c5
  [ 1501.698971] systemd-logind[2683]: New session 76 of user root.

The actions performed by the shadow code are correct, and the guest continues
without error, but the emitted error is misleading.  Tweak the comment to more
clearly identify why the condition exists, but drop the message.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>