s390x: mvpg-sie: Remove unused variable

The guest_instr variable is not used, which was likely a
copy-n-paste issue from the s390x/sie.c test.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/kvm/6b4b6ae0-6cee-e435-189a-8657159de97f@linux.ibm.com/T/#m8390c674f1b6a9fdf8055189d039c60c99a6899a


Message-Id: <20211007072136.768459-1-thuth@redhat.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>