KVM: selftests: Enhance handling WRMSR ICR register in x2APIC mode

Hardware would directly write x2APIC ICR register instead of software
emulation in some circumstances, e.g when Intel IPI virtualization is
enabled. This behavior requires normal reserved bits checking to ensure
them input as zero, otherwise it will cause #GP. So we need mask out
those reserved bits from the data written to vICR register.

Remove Delivery Status bit emulation in test case as this flag
is invalid and not needed in x2APIC mode. KVM may ignore clearing
it during interrupt dispatch which will lead to fake test failure.

Opportunistically correct vector number for test sending IPI to
non-existent vCPUs.

Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Message-Id: <20220623094511.26066-1-guang.zeng@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>