MIPS: Select HAVE_KVM for MIPS64_R{2,6}

We are now able to support KVM T&E with MIPS32 guests on some MIPS64r2
and MIPS64r6 hosts, so select HAVE_KVM so it can be enabled.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>