[CodeGen] Fix assertion failure in EmitCallArg.

The assertion was failing when a method of a parameterized class was
called and the types of the argument and parameter didn't match. To fix
the failure, move the assertion in EmitCallArg to its only caller
EmitCallArgs and require the argument and parameter types match only
when the method is not parameterized.

rdar://problem/32874473

Differential Revision: https://reviews.llvm.org/D34665

llvm-svn: 306494