More cleanup for NEON:

* Use "S" abbreviation for scalar single FP registers in class and pattern
names, instead of keeping the "D" (for "double") abbreviation and tacking on
an "s" elsewhere in the name.
* Move the scalar single FP register classes and patterns to be more
consistent with other definitions in the file.
* Rename "VNEGf32d" definition to "VNEGfd" for consistency.
* Deleted the N2VDIntsPat pattern; N2VSPat is good enough.

llvm-svn: 96521