[X86] Swap the 0 and the fudge factor in the constant pool for the 32-bit mode...

[X86] Swap the 0 and the fudge factor in the constant pool for the 32-bit mode i64->f32/f64/f80 uint_to_fp algorithm.

This allows us to generate better code for selecting the fixup
to load.

Previously when the sign was set we had to load offset 0. And
when it was clear we had to load offset 4. This required a testl,
setns, zero extend, and finally a mul by 4. By switching the offsets
we can just shift the sign bit into the lsb and multiply it by 4.