MAINTAINERS: update email address of Christian Borntraeger

My borntraeger@de.ibm.com email is just a forwarder to the
linux.ibm.com address. Let us remove the extra hop to avoid
a potential source of errors.

While at it, add the relevant email addresses to mailmap.

Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Message-Id: <20211126102449.287524-1-borntraeger@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.mailmap

@@ -50,6 +50,7 @@ Aleksandar Rikalo <aleksandar.rikalo@syrmia.com> <arikalo@wavecomp.com>
 Aleksandar Rikalo <aleksandar.rikalo@syrmia.com> <aleksandar.rikalo@rt-rk.com>
 Alexander Graf <agraf@csgraf.de> <agraf@suse.de>
 Anthony Liguori <anthony@codemonkey.ws> Anthony Liguori <aliguori@us.ibm.com>
+Christian Borntraeger <borntraeger@linux.ibm.com> <borntraeger@de.ibm.com>
 Filip Bozuta <filip.bozuta@syrmia.com> <filip.bozuta@rt-rk.com.com>
 Frederic Konrad <konrad@adacore.com> <fred.konrad@greensocs.com>
 Greg Kurz <groug@kaod.org> <gkurz@linux.vnet.ibm.com>

MAINTAINERS

@@ -393,7 +393,7 @@ F: target/ppc/kvm.c
 
 S390 KVM CPUs
 M: Halil Pasic <pasic@linux.ibm.com>
-M: Christian Borntraeger <borntraeger@de.ibm.com>
+M: Christian Borntraeger <borntraeger@linux.ibm.com>
 S: Supported
 F: target/s390x/kvm/
 F: target/s390x/ioinst.[ch]
@@ -1527,7 +1527,7 @@ S390 Machines
 -------------
 S390 Virtio-ccw
 M: Halil Pasic <pasic@linux.ibm.com>
-M: Christian Borntraeger <borntraeger@de.ibm.com>
+M: Christian Borntraeger <borntraeger@linux.ibm.com>
 S: Supported
 F: hw/char/sclp*.[hc]
 F: hw/char/terminal3270.c
@@ -1541,7 +1541,7 @@ T: git https://github.com/borntraeger/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
 S390-ccw boot
-M: Christian Borntraeger <borntraeger@de.ibm.com>
+M: Christian Borntraeger <borntraeger@linux.ibm.com>
 M: Thomas Huth <thuth@redhat.com>
 S: Supported
 F: hw/s390x/ipl.*