[X86][X87] Tag FABS/FCHS/FSQRT/FSIN/FCOS x87 instruction scheduler classes

Atom's FABS/FCHS/FSQRT latencies taken from Agner.

Note: I just added FSIN and FCOS to the existing IIC_FSINCOS itinerary, which is actually a more costly instruction.
llvm-svn: 319175