KVM: x86: ioapic: Preserve read-only values in the redirection table

According to 82093AA (IOAPIC) manual, Remote IRR and Delivery Status are
read-only. QEMU implements the bits as RO in commit 479c2a1cb7fb
("ioapic: keep RO bits for IOAPIC entry").

Signed-off-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>