KVM: s390: Limit adapter indicator access to mapped page

KVM: s390: Limit adapter indicator access to mapped page

While we check the address for errors, we don't seem to check the bit
offsets and since they are 32 and 64 bits a lot of memory can be
reached indirectly via those offsets.

Fixes: 84223598778b ("KVM: s390: irq routing for adapter interrupts.")
Suggested-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>