MIPS: KVM: Drop some unused definitions from kvm_host.h

MIPS: KVM: Drop some unused definitions from kvm_host.h

Some definitions in the MIPS asm/kvm_host.h are completely unused, so
lets drop them.

MS_TO_NS is no longer used since commit e30492bbe95a ("MIPS: KVM:
Rewrite count/compare timer emulation"). The others don't appear ever to
have been used.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11884/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>