Stop test/CodeGen/X86/v4i32load-crash.ll targeting non-X86-64 targets.

Summary:
Fixes an issue where a test attempts to use -mcpu=x86-64 on non-X86-64 targets.
This triggers an assertion in the MIPS backend since it doesn't know what ABI to
use by default for unrecognized processors.

CC: llvm-commits, rafael

Differential Revision: http://llvm-reviews.chandlerc.com/D2877