MIPS: KVM/locore.S: Don't preserve host ASID around vcpu_run

MIPS: KVM/locore.S: Don't preserve host ASID around vcpu_run

MIPS KVM uses different ASIDs for guest execution than for the host.
The host ASID is saved on the stack when entering the guest with
__kvm_mips_vcpu_run(), and restored again before returning back to the
caller (exit to userland).

- This does not take into account that pre-emption may have taken place
  during that time, which may have started a new ASID cycle and resulted
  in that process' ASID being invalidated and reused.

- This does not take into account that the process may have migrated to
  a different CPU during that time, with a different ASID assignment
  since they are managed per-CPU.

- It is actually redundant, since the host ASID will be restored
  correctly by kvm_arch_vcpu_put(), which is called almost immediately
  after kvm_arch_vcpu_ioctl_run() returns.

Therefore drop this code from locore.S

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13206/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>