[X86] Restrict vselect handling in scalarizeExtEltFP to only case to pre type...

[X86] Restrict vselect handling in scalarizeExtEltFP to only case to pre type legalization where the setcc result type is vXi1.

If the vector setcc has been legalized then we will need to convert a vector boolean of 0 or -1 to a scalar boolean of 0 or 1.

The added test case previously crashed in 32-bit mode by creating a setcc with an i64 condition that type legalization couldn't expand.

llvm-svn: 358218