[X86] Add a DAG combine to turn vzmovl+load into vzload if the load isn't...

[X86] Add a DAG combine to turn vzmovl+load into vzload if the load isn't volatile. Remove isel patterns for vzmovl+load

We currently have some isel patterns for treating vzmovl+load the same as vzload, but that shrinks the load which we shouldn't do if the load is volatile.

Rather than adding isel checks for volatile. This patch removes the patterns and teachs DAG combine to merge them into vzload when its legal to do so.

Differential Revision: https://reviews.llvm.org/D63665

llvm-svn: 364333