The prototype for kvm_check_iopl appeared in commit
f850e2e6 ("KVM: x86 emulator: Check IOPL
level during io instruction emulation"), but the function never actually
existed.  Remove the prototype.
Signed-off-by: NJosh Triplett <josh@joshtriplett.org>
Signed-off-by: NGleb Natapov <gleb@redhat.com>