[x86, SSE] change patterns for CMPP to float types to allow matching with SSE1 (PR28044)

This patch is intended to solve:
https://llvm.org/bugs/show_bug.cgi?id=28044

By changing the definition of X86ISD::CMPP to use float types, we allow it to be created 
and pass legalization for an SSE1-only target where v4i32 is not legal.

The motivational trail for this change includes:
https://llvm.org/bugs/show_bug.cgi?id=28001

and eventually makes this trigger:
http://reviews.llvm.org/D21190

Ie, after this step, we should be free to have Clang generate FP compare IR instead of x86
intrinsics for SSE C packed compare intrinsics. (We can auto-upgrade and remove the LLVM 
sse.cmp intrinsics as a follow-up step.) Once we're generating vector IR instead of x86
intrinsics, a big pile of generic optimizations can trigger.

Differential Revision: http://reviews.llvm.org/D21235

llvm-svn: 272511