MAINTAINERS: add Vasily Gorbik and Christian Borntraeger for s390

Add Vasily Gorbik and Christian Borntraeger as additional maintainers
for s390.
Acked-by: NVasily Gorbik <gor@linux.ibm.com>
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>

MAINTAINERS

@@ -3050,6 +3050,8 @@ F:	arch/riscv/net/
 
 BPF JIT for S390
 M:	Heiko Carstens <heiko.carstens@de.ibm.com>
+M:	Vasily Gorbik <gor@linux.ibm.com>
+M:	Christian Borntraeger <borntraeger@de.ibm.com>
 L:	netdev@vger.kernel.org
 L:	bpf@vger.kernel.org
 S:	Maintained
@@ -13616,6 +13618,8 @@ F:	drivers/video/fbdev/savage/
 
 S390
 M:	Heiko Carstens <heiko.carstens@de.ibm.com>
+M:	Vasily Gorbik <gor@linux.ibm.com>
+M:	Christian Borntraeger <borntraeger@de.ibm.com>
 L:	linux-s390@vger.kernel.org
 W:	http://www.ibm.com/developerworks/linux/linux390/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git