KVM: selftests: Test behavior of HWCR, a.k.a. MSR_K7_HWCR

KVM: selftests: Test behavior of HWCR, a.k.a. MSR_K7_HWCR

Verify the following behavior holds true for writes and reads of HWCR from
host userspace:

* Attempts to set bits 3, 6, or 8 are ignored
* Bits 18 and 24 are the only bits that can be set
* Any bit that can be set can also be cleared

Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20230929230246.1954854-4-jmattson@google.com
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>