[ARM][PR69194] Fix ICE in in extract_insn

[Jim Wilson]

Here is a smaller simpler testcase.  Only the first four args get
passed in regs, so the fifth one has address equal to the virtual
incoming args reg which triggers the failure.

typedef __simd128_float32_t float32x4_t;
float32x4_t
sub (float32x4_t a, float32x4_t b, float32x4_t c, float32x4_t d, float32x4_t e)
{
  return __builtin_neon_vld1v4sf((const float *)&e);
}

The original testcase failed with linaro gcc 4.9.  I verified that
this testcase fails with FSF gcc-5.3.0.

Jim