[X86] Remove unnecessary isel pattern that is a combination of two other patterns.

The pattern was this

 def : Pat<(i32 (zext (i8 (bitconvert (v8i1 VK8:$src))))),
           (MOVZX32rr8 (EXTRACT_SUBREG (i32 (COPY_TO_REGCLASS VK8:$src, GR32)), sub_8bit))>, Requires<[NoDQI]>;

but if you just let (i32 (zext X)) match byte itself you'll get MOVZX32rr8. And if you let (i8 (bitconvert (v8i1 VK8:$src))) match by itself you'll get (EXTRACT_SUBREG (i32 (COPY_TO_REGCLASS VK8:$src, GR32)), sub_8bit).

So we can just let isel do the two patterns naturally.

llvm-svn: 322049