KVM: MIPS/T&E: Report correct dcache line size

Octeon CPUs don't report the correct dcache line size in CP0_Config1.DL,
so encode the correct value for the guest CP0_Config1.DL based on
cpu_dcache_line_size().

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Daney <david.daney@cavium.com>
Cc: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org