[X86][FastISel] Use a COPY from K register to a GPR instead of a K operation

The KORTEST was introduced due to a bug where a TEST instruction used a K register.
but, turns out that the opposite case of KORTEST using a GPR is now happening

The change removes the KORTEST flow and adds a COPY instruction from the K reg to a GPR.

Differential Revision: https://reviews.llvm.org/D24953

llvm-svn: 282580