Add error reporting if the wrong type of kernel is provided for the
current mode of acceleration.

Currently a KVM kernel linked at 0x40000000 can't be used with TCG, and
a normal kernel linked at 0x80000000 can't be used with KVM.

Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>