RFR(XS) 8029464: assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) || ft->isa_narrowoop()

[Vladimir Kozlov]

https://bugs.openjdk.java.net/browse/JDK-8029464
http://cr.openjdk.java.net/~kvn/8029464/webrev/

Fix the assert check for narrow klass pointer.

Thanks to Roland for finding the cause and suggested fix.

Thanks,
Vladimir